Decode Base64 data in Java

Question

I have an image that is Base64 encoded  What is the best way to decode that in Java  Hopefully using only the libraries included with Sun Java 6

User · Answer

In a code compiled with Java 7 but potentially running in a higher java version, it seems useful to detect presence of java.util.Base64 class and use the approach best for given JVM mentioned in other questions here.

I used this code:

private static final Method JAVA_UTIL_BASE64_GETENCODER;

static {
    Method getEncoderMethod;
    try {
        final Class<?> base64Class = Class.forName("java.util.Base64");
        getEncoderMethod = base64Class.getMethod("getEncoder");
    } catch (ClassNotFoundException | NoSuchMethodException e) {
        getEncoderMethod = null;
    }
    JAVA_UTIL_BASE64_GETENCODER = getEncoderMethod;
}

static String base64EncodeToString(String s) {
    final byte[] bytes = s.getBytes(StandardCharsets.ISO_8859_1);
    if (JAVA_UTIL_BASE64_GETENCODER == null) {
        // Java 7 and older // TODO: remove this branch after switching to Java 8
        return DatatypeConverter.printBase64Binary(bytes);
    } else {
        // Java 8 and newer
        try {
            final Object encoder = JAVA_UTIL_BASE64_GETENCODER.invoke(null);
            final Class<?> encoderClass = encoder.getClass();
            final Method encodeMethod = encoderClass.getMethod("encode", byte[].class);
            final byte[] encodedBytes = (byte[]) encodeMethod.invoke(encoder, bytes);
            return new String(encodedBytes);
        } catch (NoSuchMethodException | IllegalAccessException | InvocationTargetException e) {
            throw new IllegalStateException(e);
        }
    }
}

User · Answer

import java io UnsupportedEncodingException  import java security MessageDigest  import java security NoSuchAlgorithmException  import java util Arrays  import java util Base64   import javax crypto Cipher  import javax crypto spec SecretKeySpec               author Vaquar khan            public class AES        private static SecretKeySpec secretKey      private static final String VK secretKey    VaquarKhan-secrate-key           private static byte   key                           param myKey             public static void setKey String myKey            MessageDigest sha   null          try               key   myKey getBytes  UTF-8                sha   MessageDigest getInstance  SHA-1                key   sha digest key               key   Arrays copyOf key  16               secretKey   new SecretKeySpec key   AES              catch  NoSuchAlgorithmException e                e printStackTrace              catch  UnsupportedEncodingException e                e printStackTrace                           encrypt     param strToEncrypt     param secret     return         public static String encrypt String strToEncrypt  String secret            try               setKey secret               Cipher cipher   Cipher getInstance  AES ECB PKCS5Padding                cipher init Cipher ENCRYPT MODE  secretKey               return Base64 getEncoder   encodeToString cipher doFinal strToEncrypt getBytes  UTF-8                catch  Exception e                System out println  Error while encrypting      e toString                       return null               decrypt     param strToDecrypt     param secret     return         public static String decrypt String strToDecrypt  String secret            try               setKey secret               Cipher cipher   Cipher getInstance  AES ECB PKCS5PADDING                cipher init Cipher DECRYPT MODE  secretKey               return new String cipher doFinal Base64 getDecoder   decode strToDecrypt               catch  Exception e                System out println  Error while decrypting      e toString                       return null             public static void main String   args            final String secretKey   VK secretKey          String password    VKhan 12                      String encryptedString   AES encrypt password  secretKey           String decryptedString   AES decrypt encryptedString  secretKey                      System out println password           System out println encryptedString           System out println decryptedString

User · Answer

Using Java 8 -      public static String encodeString String plainString            return  Base64 getEncoder   encodeToString plainString getBytes                public static String decodeString String encodedString            byte   bytes   Base64 getDecoder   decode encodedString           return new String bytes

User · Answer

If You are prefering performance based solution then you can use  MiGBase64   http   migbase64 sourceforge net   public class Base64Test       public static void main String   args        String encodeToString   Base64 encodeToString  JavaTips net  getBytes    true       System out println  encodeToString     encodeToString       byte   decodedBytes   Base64 decode encodeToString getBytes         System out println  decodedBytes     new String decodedBytes

User · Answer

As of v6  Java SE ships with JAXB  javax xml bind DatatypeConverter has static methods that make this easy  See parseBase64Binary   and printBase64Binary

User · Answer

Specifically in Commons Codec  class Base64 to decode byte   array  or encode byte   array

User · Answer

Here s my own implementation  if it could be useful to someone     public class Base64Coder           The line separator string of the operating system      private static final String systemLineSeparator   System getProperty  line separator            Mapping table from 6-bit nibbles to Base64 characters      private static final char   map1   new char 64          static             int i 0            for  char c  A   c lt   Z   c    map1 i      c            for  char c  a   c lt   z   c    map1 i      c            for  char c  0   c lt   9   c    map1 i      c            map1 i           map1 i                     Mapping table from Base64 characters to 6-bit nibbles      private static final byte   map2   new byte 128          static             for  int i 0  i lt map2 length  i    map2 i    -1            for  int i 0  i lt 64  i    map2 map1 i      byte i                   Encodes a string into Base64 format        No blanks or line breaks are inserted         param s  A String to be encoded         return   A String containing the Base64 encoded data             public static String encodeString  String s           return new String encode s getBytes                       Encodes a byte array into Base 64 format and breaks the output into lines of 76 characters        This method is compatible with  lt code gt sun misc BASE64Encoder encodeBuffer byte    lt  code gt          param in  An array containing the data bytes to be encoded         return    A String containing the Base64 encoded data  broken into lines             public static String encodeLines  byte   in           return encodeLines in  0  in length  76  systemLineSeparator                    Encodes a byte array into Base 64 format and breaks the output into lines         param in            An array containing the data bytes to be encoded         param iOff          Offset of the first byte in  lt code gt in lt  code gt  to be processed         param iLen          Number of bytes to be processed in  lt code gt in lt  code gt   starting at  lt code gt iOff lt  code gt          param lineLen       Line length for the output data  Should be a multiple of 4         param lineSeparator The line separator to be used to separate the output lines         return              A String containing the Base64 encoded data  broken into lines             public static String encodeLines  byte   in  int iOff  int iLen  int lineLen  String lineSeparator           int blockLen    lineLen 3    4         if  blockLen  lt   0  throw new IllegalArgumentException           int lines    iLen blockLen-1    blockLen         int bufLen     iLen 2  3  4   lines lineSeparator length           StringBuilder buf   new StringBuilder bufLen          int ip   0         while  ip  lt  iLen              int l   Math min iLen-ip  blockLen             buf append  encode in  iOff ip  l              buf append  lineSeparator             ip    l           return buf toString                     Encodes a byte array into Base64 format        No blanks or line breaks are inserted in the output         param in  An array containing the data bytes to be encoded         return    A character array containing the Base64 encoded data             public static char   encode  byte   in           return encode in  0  in length                    Encodes a byte array into Base64 format        No blanks or line breaks are inserted in the output         param in    An array containing the data bytes to be encoded         param iLen  Number of bytes to process in  lt code gt in lt  code gt          return      A character array containing the Base64 encoded data             public static char   encode  byte   in  int iLen           return encode in  0  iLen                    Encodes a byte array into Base64 format        No blanks or line breaks are inserted in the output         param in    An array containing the data bytes to be encoded         param iOff  Offset of the first byte in  lt code gt in lt  code gt  to be processed         param iLen  Number of bytes to process in  lt code gt in lt  code gt   starting at  lt code gt iOff lt  code gt          return      A character array containing the Base64 encoded data             public static char   encode  byte   in  int iOff  int iLen           int oDataLen    iLen 4 2  3           output length without padding        int oLen     iLen 2  3  4             output length including padding        char   out   new char oLen          int ip   iOff         int iEnd   iOff   iLen         int op   0         while  ip  lt  iEnd              int i0   in ip     amp  0xff            int i1   ip  lt  iEnd   in ip     amp  0xff   0            int i2   ip  lt  iEnd   in ip     amp  0xff   0            int o0   i0  gt  gt  gt  2            int o1     i0  amp    3   lt  lt  4     i1  gt  gt  gt  4             int o2     i1  amp  0xf   lt  lt  2     i2  gt  gt  gt  6             int o3   i2  amp  0x3F            out op      map1 o0             out op      map1 o1             out op    op  lt  oDataLen   map1 o2         op              out op    op  lt  oDataLen   map1 o3         op             return out                   Decodes a string from Base64 format        No blanks or line breaks are allowed within the Base64 encoded input data         param s  A Base64 String to be decoded         return   A String containing the decoded data         throws   IllegalArgumentException If the input is not valid Base64 encoded data             public static String decodeString  String s           return new String decode s                     Decodes a byte array from Base64 format and ignores line separators  tabs and blanks        CR  LF  Tab and Space characters are ignored in the input data        This method is compatible with  lt code gt sun misc BASE64Decoder decodeBuffer String  lt  code gt          param s  A Base64 String to be decoded         return   An array containing the decoded data bytes         throws   IllegalArgumentException If the input is not valid Base64 encoded data             public static byte   decodeLines  String s           char   buf   new char s length            int p   0         for  int ip   0  ip  lt  s length    ip                char c   s charAt ip             if  c         amp  amp  c      r   amp  amp  c      n   amp  amp  c      t                buf p      c           return decode buf  0  p                    Decodes a byte array from Base64 format        No blanks or line breaks are allowed within the Base64 encoded input data         param s  A Base64 String to be decoded         return   An array containing the decoded data bytes         throws   IllegalArgumentException If the input is not valid Base64 encoded data             public static byte   decode  String s           return decode s toCharArray                      Decodes a byte array from Base64 format        No blanks or line breaks are allowed within the Base64 encoded input data         param in  A character array containing the Base64 encoded data         return    An array containing the decoded data bytes         throws    IllegalArgumentException If the input is not valid Base64 encoded data             public static byte   decode  char   in           return decode in  0  in length                    Decodes a byte array from Base64 format        No blanks or line breaks are allowed within the Base64 encoded input data         param in    A character array containing the Base64 encoded data         param iOff  Offset of the first character in  lt code gt in lt  code gt  to be processed         param iLen  Number of characters to process in  lt code gt in lt  code gt   starting at  lt code gt iOff lt  code gt          return      An array containing the decoded data bytes         throws      IllegalArgumentException If the input is not valid Base64 encoded data             public static byte   decode  char   in  int iOff  int iLen           if  iLen 4    0  throw new IllegalArgumentException   Length of Base64 encoded input string is not a multiple of 4            while  iLen  gt  0  amp  amp  in iOff iLen-1          iLen--         int oLen    iLen 3    4         byte   out   new byte oLen          int ip   iOff         int iEnd   iOff   iLen         int op   0         while  ip  lt  iEnd              int i0   in ip               int i1   in ip               int i2   ip  lt  iEnd   in ip       A             int i3   ip  lt  iEnd   in ip       A             if  i0  gt  127    i1  gt  127    i2  gt  127    i3  gt  127               throw new IllegalArgumentException   Illegal character in Base64 encoded data               int b0   map2 i0             int b1   map2 i1             int b2   map2 i2             int b3   map2 i3             if  b0  lt  0    b1  lt  0    b2  lt  0    b3  lt  0               throw new IllegalArgumentException   Illegal character in Base64 encoded data               int o0     b0        lt  lt 2     b1 gt  gt  gt 4             int o1     b1  amp  0xf  lt  lt 4     b2 gt  gt  gt 2             int o2     b2  amp    3  lt  lt 6     b3            out op       byte o0            if  op lt oLen  out op       byte o1            if  op lt oLen  out op       byte o2           return out            Dummy constructor      private Base64Coder

User · Answer

You can simply try this   byte   data   Base64 getDecoder   decode base64fileContent      Base64 getDecode    returns a Base64 Decoder that can be decoded  Then you need to decode that again using   decode

User · Answer

As an alternative to sun misc BASE64Decoder or non-core libraries  look at javax mail internet MimeUtility decode     public static byte   encode byte   b  throws Exception       ByteArrayOutputStream baos   new ByteArrayOutputStream        OutputStream b64os   MimeUtility encode baos   base64        b64os write b       b64os close        return baos toByteArray      public static byte   decode byte   b  throws Exception       ByteArrayInputStream bais   new ByteArrayInputStream b       InputStream b64is   MimeUtility decode bais   base64        byte   tmp   new byte b length       int n   b64is read tmp       byte   res   new byte n       System arraycopy tmp  0  res  0  n       return res      Link with full code  Encode Decode to from Base64

User · Answer

My solution is fastest and easiest   public class MyBase64        private final static char   ALPHABET    ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789    toCharArray         private static int    toInt     new int 128        static           for int i 0  i lt  ALPHABET length  i                 toInt ALPHABET i    i                                  Translates the specified byte array into Base64 string                 param buf the byte array  not null          return the translated Base64 string  not null              public static String encode byte   buf           int size   buf length          char   ar   new char   size   2    3    4           int a   0          int i 0          while i  lt  size               byte b0   buf i                 byte b1    i  lt  size    buf i      0              byte b2    i  lt  size    buf i      0               int mask   0x3F              ar a      ALPHABET  b0  gt  gt  2   amp  mask               ar a      ALPHABET   b0  lt  lt  4      b1  amp  0xFF   gt  gt  4    amp  mask               ar a      ALPHABET   b1  lt  lt  2      b2  amp  0xFF   gt  gt  6    amp  mask               ar a      ALPHABET b2  amp  mask                     switch size   3               case 1  ar --a                      case 2  ar --a                            return new String ar                         Translates the specified Base64 string into a byte array                 param s the Base64 string  not null          return the byte array  not null              public static byte   decode String s           int delta   s endsWith           2   s endsWith          1   0          byte   buffer   new byte s length   3 4 - delta           int mask   0xFF          int index   0          for int i 0  i lt  s length    i  4               int c0   toInt s charAt  i                 int c1   toInt s charAt  i   1                buffer index      byte    c0  lt  lt  2     c1  gt  gt  4    amp  mask               if index  gt   buffer length                   return buffer                            int c2   toInt s charAt  i   2                buffer index      byte    c1  lt  lt  4     c2  gt  gt  2    amp  mask               if index  gt   buffer length                   return buffer                            int c3   toInt s charAt  i   3                 buffer index      byte    c2  lt  lt  6    c3   amp  mask                     return buffer

User · Answer

No need to use commons--Sun ships a base64 encoder with Java   You can import it as such   import sun misc BASE64Decoder    And then use it like this   BASE64Decoder decoder   new BASE64Decoder    byte   decodedBytes   decoder decodeBuffer encodedBytes     Where encodedBytes is either a java lang String or a java io InputStream   Just beware that the sun   classes are not  officially supported  by Sun   EDIT  Who knew this would be the most controversial answer I d ever post   I do know that sun   packages are not supported or guaranteed to continue existing  and I do know about Commons and use it all the time   However  the poster asked for a class that that was  included with Sun Java 6   and that s what I was trying to answer   I agree that Commons is the best way to go in general   EDIT 2  As amir75 points out below  Java 6  ships with JAXB  which contains supported code to encode decode Base64  Please see Jeremy Ross  answer below

User · Answer

As an alternative to sun misc BASE64Decoder or non-core libraries  look at javax mail internet MimeUtility decode     public static byte   encode byte   b  throws Exception       ByteArrayOutputStream baos   new ByteArrayOutputStream        OutputStream b64os   MimeUtility encode baos   base64        b64os write b       b64os close        return baos toByteArray      public static byte   decode byte   b  throws Exception       ByteArrayInputStream bais   new ByteArrayInputStream b       InputStream b64is   MimeUtility decode bais   base64        byte   tmp   new byte b length       int n   b64is read tmp       byte   res   new byte n       System arraycopy tmp  0  res  0  n       return res      Link with full code  Encode Decode to from Base64

User · Answer

Guava now has Base64 decoding built in    Use BaseEncoding base64   decode     As for dealing with possible whitespace in input use  BaseEncoding base64   decode CharMatcher WHITESPACE removeFrom         See this discussion for more information

User · Answer

import java io UnsupportedEncodingException  import java security MessageDigest  import java security NoSuchAlgorithmException  import java util Arrays  import java util Base64   import javax crypto Cipher  import javax crypto spec SecretKeySpec               author Vaquar khan            public class AES        private static SecretKeySpec secretKey      private static final String VK secretKey    VaquarKhan-secrate-key           private static byte   key                           param myKey             public static void setKey String myKey            MessageDigest sha   null          try               key   myKey getBytes  UTF-8                sha   MessageDigest getInstance  SHA-1                key   sha digest key               key   Arrays copyOf key  16               secretKey   new SecretKeySpec key   AES              catch  NoSuchAlgorithmException e                e printStackTrace              catch  UnsupportedEncodingException e                e printStackTrace                           encrypt     param strToEncrypt     param secret     return         public static String encrypt String strToEncrypt  String secret            try               setKey secret               Cipher cipher   Cipher getInstance  AES ECB PKCS5Padding                cipher init Cipher ENCRYPT MODE  secretKey               return Base64 getEncoder   encodeToString cipher doFinal strToEncrypt getBytes  UTF-8                catch  Exception e                System out println  Error while encrypting      e toString                       return null               decrypt     param strToDecrypt     param secret     return         public static String decrypt String strToDecrypt  String secret            try               setKey secret               Cipher cipher   Cipher getInstance  AES ECB PKCS5PADDING                cipher init Cipher DECRYPT MODE  secretKey               return new String cipher doFinal Base64 getDecoder   decode strToDecrypt               catch  Exception e                System out println  Error while decrypting      e toString                       return null             public static void main String   args            final String secretKey   VK secretKey          String password    VKhan 12                      String encryptedString   AES encrypt password  secretKey           String decryptedString   AES decrypt encryptedString  secretKey                      System out println password           System out println encryptedString           System out println decryptedString

User · Answer

Guava now has Base64 decoding built in    Use BaseEncoding base64   decode     As for dealing with possible whitespace in input use  BaseEncoding base64   decode CharMatcher WHITESPACE removeFrom         See this discussion for more information

User · Answer

I used android util base64 that works pretty good without any dependances    Usage   byte   decodedKey   Base64 decode encodedPublicKey  Base64 DEFAULT       package com test   import java io UnsupportedEncodingException          Utilities for encoding and decoding the Base64 representation of    binary data   See RFCs  lt a    href  http   www ietf org rfc rfc2045 txt  gt 2045 lt  a gt  and  lt a    href  http   www ietf org rfc rfc3548 txt  gt 3548 lt  a gt       public class Base64        public static final int DEFAULT   0        public static final int NO PADDING   1        public static final int NO WRAP   2        public static final int CRLF   4        public static final int URL SAFE   8        public static final int NO CLOSE   16           --------------------------------------------------------         shared code         --------------------------------------------------------         package    static abstract class Coder           public byte   output          public int op           public abstract boolean process byte   input  int offset  int len  boolean finish             public abstract int maxOutputSize int len                  --------------------------------------------------------         decoding         --------------------------------------------------------       public static byte   decode String str  int flags            return decode str getBytes    flags              public static byte   decode byte   input  int flags            return decode input  0  input length  flags               public static byte   decode byte   input  int offset  int len  int flags               Allocate space for the most data the input could represent              It could contain less if it contains whitespace  etc           Decoder decoder   new Decoder flags  new byte len 3 4             if   decoder process input  offset  len  true                 throw new IllegalArgumentException  bad base-64                          Maybe we got lucky and allocated exactly enough output space          if  decoder op    decoder output length                return decoder output                        Need to shorten the array  so allocate a new one of the            right size and copy          byte   temp   new byte decoder op           System arraycopy decoder output  0  temp  0  decoder op           return temp            static class Decoder extends Coder                  private static final int DECODE                   -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  62  -1  -1  -1  63              52  53  54  55  56  57  58  59  60  61  -1  -1  -1  -2  -1  -1              -1   0   1   2   3   4   5   6   7   8   9  10  11  12  13  14              15  16  17  18  19  20  21  22  23  24  25  -1  -1  -1  -1  -1              -1  26  27  28  29  30  31  32  33  34  35  36  37  38  39  40              41  42  43  44  45  46  47  48  49  50  51  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1                                     Decode lookup table for the  web safe  variant  RFC 3548            sec  4  where - and   replace   and                        private static final int DECODE WEBSAFE                   -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  62  -1  -1              52  53  54  55  56  57  58  59  60  61  -1  -1  -1  -2  -1  -1              -1   0   1   2   3   4   5   6   7   8   9  10  11  12  13  14              15  16  17  18  19  20  21  22  23  24  25  -1  -1  -1  -1  63              -1  26  27  28  29  30  31  32  33  34  35  36  37  38  39  40              41  42  43  44  45  46  47  48  49  50  51  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1                          Non-data values in the DECODE arrays             private static final int SKIP   -1          private static final int EQUALS   -2            private int state       state number  0 to 6          private int value           final private int   alphabet           public Decoder int flags  byte   output                this output   output               alphabet     flags  amp  URL SAFE     0    DECODE   DECODE WEBSAFE              state   0              value   0                      public int maxOutputSize int len                return len   3 4   10                                    Decode another block of input data                         return true if the state machine is still healthy   false if                    bad base-64 data has been detected in the input stream                      public boolean process byte   input  int offset  int len  boolean finish                if  this state    6  return false               int p   offset              len    offset               int state   this state              int value   this value              int op   0              final byte   output   this output              final int   alphabet   this alphabet               while  p  lt  len                                    if  state    0                        while  p 4  lt   len  amp  amp                              value     alphabet input p   amp  0xff   lt  lt  18                                          alphabet input p 1   amp  0xff   lt  lt  12                                          alphabet input p 2   amp  0xff   lt  lt  6                                          alphabet input p 3   amp  0xff      gt   0                            output op 2     byte  value                          output op 1     byte   value  gt  gt  8                           output op     byte   value  gt  gt  16                           op    3                          p    4                                            if  p  gt   len  break                                     int d   alphabet input p     amp  0xff                    switch  state                    case 0                      if  d  gt   0                            value   d                            state                        else if  d    SKIP                            this state   6                          return false                                            break                   case 1                      if  d  gt   0                            value    value  lt  lt  6    d                            state                        else if  d    SKIP                            this state   6                          return false                                            break                   case 2                      if  d  gt   0                            value    value  lt  lt  6    d                            state                        else if  d    EQUALS                               Emit the last  partial  output tuple                             expect exactly one more padding character                          output op       byte   value  gt  gt  4                           state   4                        else if  d    SKIP                            this state   6                          return false                                            break                   case 3                      if  d  gt   0                               Emit the output triple and return to state 0                          value    value  lt  lt  6    d                          output op 2     byte  value                          output op 1     byte   value  gt  gt  8                           output op     byte   value  gt  gt  16                           op    3                          state   0                        else if  d    EQUALS                               Emit the last  partial  output tuple                             expect no further data or padding characters                          output op 1     byte   value  gt  gt  2                           output op     byte   value  gt  gt  10                           op    2                          state   5                        else if  d    SKIP                            this state   6                          return false                                            break                   case 4                      if  d    EQUALS                              state                        else if  d    SKIP                            this state   6                          return false                                            break                   case 5                      if  d    SKIP                            this state   6                          return false                                            break                                               if   finish                       We re out of input  but a future call could provide                    more                  this state   state                  this value   value                  this op   op                  return true                              switch  state                case 0                  break              case 1                  this state   6                  return false              case 2                  output op       byte   value  gt  gt  4                   break              case 3                 output op       byte   value  gt  gt  10                   output op       byte   value  gt  gt  2                   break              case 4                  this state   6                  return false              case 5                  break                             this state   state              this op   op              return true                           --------------------------------------------------------         encoding         --------------------------------------------------------         public static String encodeToString byte   input  int flags            try               return new String encode input  flags    US-ASCII              catch  UnsupportedEncodingException e                   US-ASCII is guaranteed to be available              throw new AssertionError e                         public static String encodeToString byte   input  int offset  int len  int flags            try               return new String encode input  offset  len  flags    US-ASCII              catch  UnsupportedEncodingException e                   US-ASCII is guaranteed to be available              throw new AssertionError e                         public static byte   encode byte   input  int flags            return encode input  0  input length  flags               public static byte   encode byte   input  int offset  int len  int flags            Encoder encoder   new Encoder flags  null               Compute the exact length of the array we will produce          int output len   len   3   4              Account for the tail of the data and the padding bytes  if any          if  encoder do padding                if  len   3  gt  0                    output len    4                          else               switch  len   3                    case 0  break                  case 1  output len    2  break                  case 2  output len    3  break                                      Account for the newlines  if any          if  encoder do newline  amp  amp  len  gt  0                output len       len-1     3   Encoder LINE GROUPS     1                     encoder do cr   2   1                      encoder output   new byte output len           encoder process input  offset  len  true            assert encoder op    output len           return encoder output                package    static class Encoder extends Coder                          Emit a new line every this many output tuples   Corresponds to            a 76-character line length  the maximum allowable according to             lt a href  http   www ietf org rfc rfc2045 txt  gt RFC 2045 lt  a gt                        public static final int LINE GROUPS   19                          Lookup table for turning Base64 alphabet positions  6 bits             into output bytes                      private static final byte ENCODE                    A    B    C    D    E    F    G    H    I    J    K    L    M    N    O    P                Q    R    S    T    U    V    W    X    Y    Z    a    b    c    d    e    f                g    h    i    j    k    l    m    n    o    p    q    r    s    t    u    v                w    x    y    z    0    1    2    3    4    5    6    7    8    9                                                Lookup table for turning Base64 alphabet positions  6 bits             into output bytes                      private static final byte ENCODE WEBSAFE                    A    B    C    D    E    F    G    H    I    J    K    L    M    N    O    P                Q    R    S    T    U    V    W    X    Y    Z    a    b    c    d    e    f                g    h    i    j    k    l    m    n    o    p    q    r    s    t    u    v                w    x    y    z    0    1    2    3    4    5    6    7    8    9    -                            final private byte   tail             package    int tailLen          private int count           final public boolean do padding          final public boolean do newline          final public boolean do cr          final private byte   alphabet           public Encoder int flags  byte   output                this output   output               do padding    flags  amp  NO PADDING     0              do newline    flags  amp  NO WRAP     0              do cr    flags  amp  CRLF     0              alphabet     flags  amp  URL SAFE     0    ENCODE   ENCODE WEBSAFE               tail   new byte 2               tailLen   0               count   do newline   LINE GROUPS   -1                                     return an overestimate for the number of bytes   code            len  bytes could encode to                      public int maxOutputSize int len                return len   8 5   10                     public boolean process byte   input  int offset  int len  boolean finish                   Using local variables makes the encoder about 9  faster              final byte   alphabet   this alphabet              final byte   output   this output              int op   0              int count   this count               int p   offset              len    offset              int v   -1                  First we need to concatenate the tail of the previous call                with any input bytes available now and see if we can empty                the tail               switch  tailLen                    case 0                         There was no tail                      break                   case 1                      if  p 2  lt   len                               A 1-byte tail with at least 2 bytes of                            input available now                          v     tail 0   amp  0xff   lt  lt  16                                  input p     amp  0xff   lt  lt  8                                 input p     amp  0xff                           tailLen   0                                             break                   case 2                      if  p 1  lt   len                               A 2-byte tail with at least 1 byte of input                          v     tail 0   amp  0xff   lt  lt  16                                  tail 1   amp  0xff   lt  lt  8                                 input p     amp  0xff                           tailLen   0                                            break                             if  v    -1                    output op      alphabet  v  gt  gt  18   amp  0x3f                   output op      alphabet  v  gt  gt  12   amp  0x3f                   output op      alphabet  v  gt  gt  6   amp  0x3f                   output op      alphabet v  amp  0x3f                   if  --count    0                        if  do cr  output op        r                       output op        n                       count   LINE GROUPS                                                  At this point either there is no tail  or there are fewer                than 3 bytes of input available                  The main loop  turning 3 input bytes into 4 output bytes on                each iteration              while  p 3  lt   len                    v     input p   amp  0xff   lt  lt  16                          input p 1   amp  0xff   lt  lt  8                         input p 2   amp  0xff                   output op    alphabet  v  gt  gt  18   amp  0x3f                   output op 1    alphabet  v  gt  gt  12   amp  0x3f                   output op 2    alphabet  v  gt  gt  6   amp  0x3f                   output op 3    alphabet v  amp  0x3f                   p    3                  op    4                  if  --count    0                        if  do cr  output op        r                       output op        n                       count   LINE GROUPS                                               if  finish                     if  p-tailLen    len-1                        int t   0                      v     tailLen  gt  0   tail t      input p      amp  0xff   lt  lt  4                      tailLen -  t                      output op      alphabet  v  gt  gt  6   amp  0x3f                       output op      alphabet v  amp  0x3f                       if  do padding                            output op                                   output op                                                     if  do newline                            if  do cr  output op        r                           output op        n                                           else if  p-tailLen    len-2                        int t   0                      v      tailLen  gt  1   tail t      input p      amp  0xff   lt  lt  10                               tailLen  gt  0   tail t      input p      amp  0xff   lt  lt  2                       tailLen -  t                      output op      alphabet  v  gt  gt  12   amp  0x3f                       output op      alphabet  v  gt  gt  6   amp  0x3f                       output op      alphabet v  amp  0x3f                       if  do padding                            output op                                                     if  do newline                            if  do cr  output op        r                           output op        n                                           else if  do newline  amp  amp  op  gt  0  amp  amp  count    LINE GROUPS                        if  do cr  output op        r                       output op        n                                      assert tailLen    0                  assert p    len                else                      Save the leftovers in tail to be consumed on the next                    call to encodeInternal                   if  p    len-1                        tail tailLen      input p                     else if  p    len-2                        tail tailLen      input p                       tail tailLen      input p 1                                                this op   op              this count   count               return true                       private Base64            don t instantiate

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Another late answer  but my benchmarking shows that Jetty s implementation of Base64 encoder is pretty fast  Not as fast as MiGBase64 but faster than iHarder Base64   import org eclipse jetty util B64Code   final String decoded   B64Code decode encoded   UTF-8      I also did some benchmarks         library          encode         decode    ------------------ -------------- -------------   MiGBase64          10146001 00    6426446 00   Jetty B64Code       8846191 00    3101361 75   iHarder Base64      3259590 50    2505280 00   Commons-Codec        241318 04     255179 96   These are runs sec so higher is better

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As an alternative to sun misc BASE64Decoder or non-core libraries  look at javax mail internet MimeUtility decode     public static byte   encode byte   b  throws Exception       ByteArrayOutputStream baos   new ByteArrayOutputStream        OutputStream b64os   MimeUtility encode baos   base64        b64os write b       b64os close        return baos toByteArray      public static byte   decode byte   b  throws Exception       ByteArrayInputStream bais   new ByteArrayInputStream b       InputStream b64is   MimeUtility decode bais   base64        byte   tmp   new byte b length       int n   b64is read tmp       byte   res   new byte n       System arraycopy tmp  0  res  0  n       return res      Link with full code  Encode Decode to from Base64

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If You are prefering performance based solution then you can use  MiGBase64   http   migbase64 sourceforge net   public class Base64Test       public static void main String   args        String encodeToString   Base64 encodeToString  JavaTips net  getBytes    true       System out println  encodeToString     encodeToString       byte   decodedBytes   Base64 decode encodeToString getBytes         System out println  decodedBytes     new String decodedBytes

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My solution is fastest and easiest   public class MyBase64        private final static char   ALPHABET    ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789    toCharArray         private static int    toInt     new int 128        static           for int i 0  i lt  ALPHABET length  i                 toInt ALPHABET i    i                                  Translates the specified byte array into Base64 string                 param buf the byte array  not null          return the translated Base64 string  not null              public static String encode byte   buf           int size   buf length          char   ar   new char   size   2    3    4           int a   0          int i 0          while i  lt  size               byte b0   buf i                 byte b1    i  lt  size    buf i      0              byte b2    i  lt  size    buf i      0               int mask   0x3F              ar a      ALPHABET  b0  gt  gt  2   amp  mask               ar a      ALPHABET   b0  lt  lt  4      b1  amp  0xFF   gt  gt  4    amp  mask               ar a      ALPHABET   b1  lt  lt  2      b2  amp  0xFF   gt  gt  6    amp  mask               ar a      ALPHABET b2  amp  mask                     switch size   3               case 1  ar --a                      case 2  ar --a                            return new String ar                         Translates the specified Base64 string into a byte array                 param s the Base64 string  not null          return the byte array  not null              public static byte   decode String s           int delta   s endsWith           2   s endsWith          1   0          byte   buffer   new byte s length   3 4 - delta           int mask   0xFF          int index   0          for int i 0  i lt  s length    i  4               int c0   toInt s charAt  i                 int c1   toInt s charAt  i   1                buffer index      byte    c0  lt  lt  2     c1  gt  gt  4    amp  mask               if index  gt   buffer length                   return buffer                            int c2   toInt s charAt  i   2                buffer index      byte    c1  lt  lt  4     c2  gt  gt  2    amp  mask               if index  gt   buffer length                   return buffer                            int c3   toInt s charAt  i   3                 buffer index      byte    c2  lt  lt  6    c3   amp  mask                     return buffer

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Hope this helps you      import com sun org apache xml internal security utils Base64  String str  Hello World   String base64 str Base64 encode str getBytes  UTF-8       Or   String str  Hello World   String base64 str     try     base64 str  String Class forName  java util prefs Base64   getDeclaredMethod  byteArrayToBase64   new Class   byte   class   invoke null  new Object   str getBytes  UTF-8           catch  Exception ee       java util prefs Base64 works on local rt jar   But it is not in The JRE Class White List  and not in Available classes not listed in the GAE J white-list  What a pity   PS  In android  it s easy because that android util Base64 has been included since Android API Level 8

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This is a late answer  but Joshua Bloch committed his Base64 class  when he was working for Sun  ahem  Oracle  under the java util prefs package  This class existed since JDK 1 4   E g   String currentString    Hello World   String base64String   java util prefs Base64 byteArrayToBase64 currentString getBytes  UTF-8

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No need to use commons--Sun ships a base64 encoder with Java   You can import it as such   import sun misc BASE64Decoder    And then use it like this   BASE64Decoder decoder   new BASE64Decoder    byte   decodedBytes   decoder decodeBuffer encodedBytes     Where encodedBytes is either a java lang String or a java io InputStream   Just beware that the sun   classes are not  officially supported  by Sun   EDIT  Who knew this would be the most controversial answer I d ever post   I do know that sun   packages are not supported or guaranteed to continue existing  and I do know about Commons and use it all the time   However  the poster asked for a class that that was  included with Sun Java 6   and that s what I was trying to answer   I agree that Commons is the best way to go in general   EDIT 2  As amir75 points out below  Java 6  ships with JAXB  which contains supported code to encode decode Base64  Please see Jeremy Ross  answer below

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Specifically in Commons Codec  class Base64 to decode byte   array  or encode byte   array

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You can write or download file from encoded Base64 string   Base64 base64   new Base64     String encodedFile  JVBERi0xLjUKJeLjz9MKMSAwIG9iago8PCAKICAgL1R5cGUgL0NhdGFsb2cKICAgL1BhZ2VzIDIgMCBSCiAgIC9QYWdlTGF5b3V0IC9TaW5                  byte   dd encodedFile getBytes                byte   bytes   Base64 decodeBase64 dd     response setHeader  Content-disposition    attachment  filename     filename                    response setHeader  Cache-Control    no-cache                response setHeader  Expires    -1                    actually send result bytes             response getOutputStream   write bytes     Worked for me and hopefully for you also

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As of Java 8  there is an officially supported API for Base64 encoding and decoding  In time this will probably become the default choice   The API includes the class java util Base64 and its nested classes  It supports three different flavors  basic  URL safe  and MIME   Sample code using the  basic  encoding   import java util Base64   byte   bytes    Hello  World   getBytes  UTF-8    String encoded   Base64 getEncoder   encodeToString bytes   byte   decoded   Base64 getDecoder   decode encoded     The documentation for java util Base64 includes several more methods for configuring encoders and decoders  and for using different classes as inputs and outputs  byte arrays  strings  ByteBuffers  java io streams

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In a code compiled with Java 7 but potentially running in a higher java version, it seems useful to detect presence of java.util.Base64 class and use the approach best for given JVM mentioned in other questions here.

I used this code:

private static final Method JAVA_UTIL_BASE64_GETENCODER;

static {
    Method getEncoderMethod;
    try {
        final Class<?> base64Class = Class.forName("java.util.Base64");
        getEncoderMethod = base64Class.getMethod("getEncoder");
    } catch (ClassNotFoundException | NoSuchMethodException e) {
        getEncoderMethod = null;
    }
    JAVA_UTIL_BASE64_GETENCODER = getEncoderMethod;
}

static String base64EncodeToString(String s) {
    final byte[] bytes = s.getBytes(StandardCharsets.ISO_8859_1);
    if (JAVA_UTIL_BASE64_GETENCODER == null) {
        // Java 7 and older // TODO: remove this branch after switching to Java 8
        return DatatypeConverter.printBase64Binary(bytes);
    } else {
        // Java 8 and newer
        try {
            final Object encoder = JAVA_UTIL_BASE64_GETENCODER.invoke(null);
            final Class<?> encoderClass = encoder.getClass();
            final Method encodeMethod = encoderClass.getMethod("encode", byte[].class);
            final byte[] encodedBytes = (byte[]) encodeMethod.invoke(encoder, bytes);
            return new String(encodedBytes);
        } catch (NoSuchMethodException | IllegalAccessException | InvocationTargetException e) {
            throw new IllegalStateException(e);
        }
    }
}

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Specifically in Commons Codec  class Base64 to decode byte   array  or encode byte   array

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Using Java 8 -      public static String encodeString String plainString            return  Base64 getEncoder   encodeToString plainString getBytes                public static String decodeString String encodedString            byte   bytes   Base64 getDecoder   decode encodedString           return new String bytes

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The Java 8 implementation of java util Base64 has no dependencies on other Java 8 specific classes   I am not certain if this will work for Java 6 project  but it is possible to copy and paste the Base64 java file into a Java 7 project and compile it with no modification other than importing java util Arrays and java util Objects   Note the Base64 java file is covered by the GNU GPL2

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You can write or download file from encoded Base64 string   Base64 base64   new Base64     String encodedFile  JVBERi0xLjUKJeLjz9MKMSAwIG9iago8PCAKICAgL1R5cGUgL0NhdGFsb2cKICAgL1BhZ2VzIDIgMCBSCiAgIC9QYWdlTGF5b3V0IC9TaW5                  byte   dd encodedFile getBytes                byte   bytes   Base64 decodeBase64 dd     response setHeader  Content-disposition    attachment  filename     filename                    response setHeader  Cache-Control    no-cache                response setHeader  Expires    -1                    actually send result bytes             response getOutputStream   write bytes     Worked for me and hopefully for you also

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Another late answer  but my benchmarking shows that Jetty s implementation of Base64 encoder is pretty fast  Not as fast as MiGBase64 but faster than iHarder Base64   import org eclipse jetty util B64Code   final String decoded   B64Code decode encoded   UTF-8      I also did some benchmarks         library          encode         decode    ------------------ -------------- -------------   MiGBase64          10146001 00    6426446 00   Jetty B64Code       8846191 00    3101361 75   iHarder Base64      3259590 50    2505280 00   Commons-Codec        241318 04     255179 96   These are runs sec so higher is better

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Specifically in Commons Codec  class Base64 to decode byte   array  or encode byte   array

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No need to use commons--Sun ships a base64 encoder with Java   You can import it as such   import sun misc BASE64Decoder    And then use it like this   BASE64Decoder decoder   new BASE64Decoder    byte   decodedBytes   decoder decodeBuffer encodedBytes     Where encodedBytes is either a java lang String or a java io InputStream   Just beware that the sun   classes are not  officially supported  by Sun   EDIT  Who knew this would be the most controversial answer I d ever post   I do know that sun   packages are not supported or guaranteed to continue existing  and I do know about Commons and use it all the time   However  the poster asked for a class that that was  included with Sun Java 6   and that s what I was trying to answer   I agree that Commons is the best way to go in general   EDIT 2  As amir75 points out below  Java 6  ships with JAXB  which contains supported code to encode decode Base64  Please see Jeremy Ross  answer below

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You can simply try this   byte   data   Base64 getDecoder   decode base64fileContent      Base64 getDecode    returns a Base64 Decoder that can be decoded  Then you need to decode that again using   decode

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As an alternative to sun misc BASE64Decoder or non-core libraries  look at javax mail internet MimeUtility decode     public static byte   encode byte   b  throws Exception       ByteArrayOutputStream baos   new ByteArrayOutputStream        OutputStream b64os   MimeUtility encode baos   base64        b64os write b       b64os close        return baos toByteArray      public static byte   decode byte   b  throws Exception       ByteArrayInputStream bais   new ByteArrayInputStream b       InputStream b64is   MimeUtility decode bais   base64        byte   tmp   new byte b length       int n   b64is read tmp       byte   res   new byte n       System arraycopy tmp  0  res  0  n       return res      Link with full code  Encode Decode to from Base64

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Given a test encode decode example of javax xml bind DatatypeConverter using methods parseBase64Binary   and printBase64Binary   referring to  jeremy-ross and  nightfirecat answer    Test public void EncodeDecode           ENCODE     String hello    Hello World       byte   helloBytes   hello getBytes StandardCharsets UTF 8       String encodedHello   DatatypeConverter printBase64Binary helloBytes       LOGGER info hello     encoded  gt      encodedHello          DECODE     byte   encodedHelloBytes   DatatypeConverter parseBase64Binary encodedHello       String helloAgain   new String encodedHelloBytes  StandardCharsets UTF 8        LOGGER info encodedHello     decoded  gt      helloAgain        Assert assertEquals hello  helloAgain       Result   INFO - Hello World encoded  gt  SGVsbG8gV29ybGQ  INFO - SGVsbG8gV29ybGQ  decoded  gt  Hello World

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The Java 8 implementation of java util Base64 has no dependencies on other Java 8 specific classes   I am not certain if this will work for Java 6 project  but it is possible to copy and paste the Base64 java file into a Java 7 project and compile it with no modification other than importing java util Arrays and java util Objects   Note the Base64 java file is covered by the GNU GPL2

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As of v6  Java SE ships with JAXB  javax xml bind DatatypeConverter has static methods that make this easy  See parseBase64Binary   and printBase64Binary

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As of Java 8  there is an officially supported API for Base64 encoding and decoding  In time this will probably become the default choice   The API includes the class java util Base64 and its nested classes  It supports three different flavors  basic  URL safe  and MIME   Sample code using the  basic  encoding   import java util Base64   byte   bytes    Hello  World   getBytes  UTF-8    String encoded   Base64 getEncoder   encodeToString bytes   byte   decoded   Base64 getDecoder   decode encoded     The documentation for java util Base64 includes several more methods for configuring encoders and decoders  and for using different classes as inputs and outputs  byte arrays  strings  ByteBuffers  java io streams

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Hope this helps you      import com sun org apache xml internal security utils Base64  String str  Hello World   String base64 str Base64 encode str getBytes  UTF-8       Or   String str  Hello World   String base64 str     try     base64 str  String Class forName  java util prefs Base64   getDeclaredMethod  byteArrayToBase64   new Class   byte   class   invoke null  new Object   str getBytes  UTF-8           catch  Exception ee       java util prefs Base64 works on local rt jar   But it is not in The JRE Class White List  and not in Available classes not listed in the GAE J white-list  What a pity   PS  In android  it s easy because that android util Base64 has been included since Android API Level 8

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Here s my own implementation  if it could be useful to someone     public class Base64Coder           The line separator string of the operating system      private static final String systemLineSeparator   System getProperty  line separator            Mapping table from 6-bit nibbles to Base64 characters      private static final char   map1   new char 64          static             int i 0            for  char c  A   c lt   Z   c    map1 i      c            for  char c  a   c lt   z   c    map1 i      c            for  char c  0   c lt   9   c    map1 i      c            map1 i           map1 i                     Mapping table from Base64 characters to 6-bit nibbles      private static final byte   map2   new byte 128          static             for  int i 0  i lt map2 length  i    map2 i    -1            for  int i 0  i lt 64  i    map2 map1 i      byte i                   Encodes a string into Base64 format        No blanks or line breaks are inserted         param s  A String to be encoded         return   A String containing the Base64 encoded data             public static String encodeString  String s           return new String encode s getBytes                       Encodes a byte array into Base 64 format and breaks the output into lines of 76 characters        This method is compatible with  lt code gt sun misc BASE64Encoder encodeBuffer byte    lt  code gt          param in  An array containing the data bytes to be encoded         return    A String containing the Base64 encoded data  broken into lines             public static String encodeLines  byte   in           return encodeLines in  0  in length  76  systemLineSeparator                    Encodes a byte array into Base 64 format and breaks the output into lines         param in            An array containing the data bytes to be encoded         param iOff          Offset of the first byte in  lt code gt in lt  code gt  to be processed         param iLen          Number of bytes to be processed in  lt code gt in lt  code gt   starting at  lt code gt iOff lt  code gt          param lineLen       Line length for the output data  Should be a multiple of 4         param lineSeparator The line separator to be used to separate the output lines         return              A String containing the Base64 encoded data  broken into lines             public static String encodeLines  byte   in  int iOff  int iLen  int lineLen  String lineSeparator           int blockLen    lineLen 3    4         if  blockLen  lt   0  throw new IllegalArgumentException           int lines    iLen blockLen-1    blockLen         int bufLen     iLen 2  3  4   lines lineSeparator length           StringBuilder buf   new StringBuilder bufLen          int ip   0         while  ip  lt  iLen              int l   Math min iLen-ip  blockLen             buf append  encode in  iOff ip  l              buf append  lineSeparator             ip    l           return buf toString                     Encodes a byte array into Base64 format        No blanks or line breaks are inserted in the output         param in  An array containing the data bytes to be encoded         return    A character array containing the Base64 encoded data             public static char   encode  byte   in           return encode in  0  in length                    Encodes a byte array into Base64 format        No blanks or line breaks are inserted in the output         param in    An array containing the data bytes to be encoded         param iLen  Number of bytes to process in  lt code gt in lt  code gt          return      A character array containing the Base64 encoded data             public static char   encode  byte   in  int iLen           return encode in  0  iLen                    Encodes a byte array into Base64 format        No blanks or line breaks are inserted in the output         param in    An array containing the data bytes to be encoded         param iOff  Offset of the first byte in  lt code gt in lt  code gt  to be processed         param iLen  Number of bytes to process in  lt code gt in lt  code gt   starting at  lt code gt iOff lt  code gt          return      A character array containing the Base64 encoded data             public static char   encode  byte   in  int iOff  int iLen           int oDataLen    iLen 4 2  3           output length without padding        int oLen     iLen 2  3  4             output length including padding        char   out   new char oLen          int ip   iOff         int iEnd   iOff   iLen         int op   0         while  ip  lt  iEnd              int i0   in ip     amp  0xff            int i1   ip  lt  iEnd   in ip     amp  0xff   0            int i2   ip  lt  iEnd   in ip     amp  0xff   0            int o0   i0  gt  gt  gt  2            int o1     i0  amp    3   lt  lt  4     i1  gt  gt  gt  4             int o2     i1  amp  0xf   lt  lt  2     i2  gt  gt  gt  6             int o3   i2  amp  0x3F            out op      map1 o0             out op      map1 o1             out op    op  lt  oDataLen   map1 o2         op              out op    op  lt  oDataLen   map1 o3         op             return out                   Decodes a string from Base64 format        No blanks or line breaks are allowed within the Base64 encoded input data         param s  A Base64 String to be decoded         return   A String containing the decoded data         throws   IllegalArgumentException If the input is not valid Base64 encoded data             public static String decodeString  String s           return new String decode s                     Decodes a byte array from Base64 format and ignores line separators  tabs and blanks        CR  LF  Tab and Space characters are ignored in the input data        This method is compatible with  lt code gt sun misc BASE64Decoder decodeBuffer String  lt  code gt          param s  A Base64 String to be decoded         return   An array containing the decoded data bytes         throws   IllegalArgumentException If the input is not valid Base64 encoded data             public static byte   decodeLines  String s           char   buf   new char s length            int p   0         for  int ip   0  ip  lt  s length    ip                char c   s charAt ip             if  c         amp  amp  c      r   amp  amp  c      n   amp  amp  c      t                buf p      c           return decode buf  0  p                    Decodes a byte array from Base64 format        No blanks or line breaks are allowed within the Base64 encoded input data         param s  A Base64 String to be decoded         return   An array containing the decoded data bytes         throws   IllegalArgumentException If the input is not valid Base64 encoded data             public static byte   decode  String s           return decode s toCharArray                      Decodes a byte array from Base64 format        No blanks or line breaks are allowed within the Base64 encoded input data         param in  A character array containing the Base64 encoded data         return    An array containing the decoded data bytes         throws    IllegalArgumentException If the input is not valid Base64 encoded data             public static byte   decode  char   in           return decode in  0  in length                    Decodes a byte array from Base64 format        No blanks or line breaks are allowed within the Base64 encoded input data         param in    A character array containing the Base64 encoded data         param iOff  Offset of the first character in  lt code gt in lt  code gt  to be processed         param iLen  Number of characters to process in  lt code gt in lt  code gt   starting at  lt code gt iOff lt  code gt          return      An array containing the decoded data bytes         throws      IllegalArgumentException If the input is not valid Base64 encoded data             public static byte   decode  char   in  int iOff  int iLen           if  iLen 4    0  throw new IllegalArgumentException   Length of Base64 encoded input string is not a multiple of 4            while  iLen  gt  0  amp  amp  in iOff iLen-1          iLen--         int oLen    iLen 3    4         byte   out   new byte oLen          int ip   iOff         int iEnd   iOff   iLen         int op   0         while  ip  lt  iEnd              int i0   in ip               int i1   in ip               int i2   ip  lt  iEnd   in ip       A             int i3   ip  lt  iEnd   in ip       A             if  i0  gt  127    i1  gt  127    i2  gt  127    i3  gt  127               throw new IllegalArgumentException   Illegal character in Base64 encoded data               int b0   map2 i0             int b1   map2 i1             int b2   map2 i2             int b3   map2 i3             if  b0  lt  0    b1  lt  0    b2  lt  0    b3  lt  0               throw new IllegalArgumentException   Illegal character in Base64 encoded data               int o0     b0        lt  lt 2     b1 gt  gt  gt 4             int o1     b1  amp  0xf  lt  lt 4     b2 gt  gt  gt 2             int o2     b2  amp    3  lt  lt 6     b3            out op       byte o0            if  op lt oLen  out op       byte o1            if  op lt oLen  out op       byte o2           return out            Dummy constructor      private Base64Coder

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This is a late answer  but Joshua Bloch committed his Base64 class  when he was working for Sun  ahem  Oracle  under the java util prefs package  This class existed since JDK 1 4   E g   String currentString    Hello World   String base64String   java util prefs Base64 byteArrayToBase64 currentString getBytes  UTF-8

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I used android util base64 that works pretty good without any dependances    Usage   byte   decodedKey   Base64 decode encodedPublicKey  Base64 DEFAULT       package com test   import java io UnsupportedEncodingException          Utilities for encoding and decoding the Base64 representation of    binary data   See RFCs  lt a    href  http   www ietf org rfc rfc2045 txt  gt 2045 lt  a gt  and  lt a    href  http   www ietf org rfc rfc3548 txt  gt 3548 lt  a gt       public class Base64        public static final int DEFAULT   0        public static final int NO PADDING   1        public static final int NO WRAP   2        public static final int CRLF   4        public static final int URL SAFE   8        public static final int NO CLOSE   16           --------------------------------------------------------         shared code         --------------------------------------------------------         package    static abstract class Coder           public byte   output          public int op           public abstract boolean process byte   input  int offset  int len  boolean finish             public abstract int maxOutputSize int len                  --------------------------------------------------------         decoding         --------------------------------------------------------       public static byte   decode String str  int flags            return decode str getBytes    flags              public static byte   decode byte   input  int flags            return decode input  0  input length  flags               public static byte   decode byte   input  int offset  int len  int flags               Allocate space for the most data the input could represent              It could contain less if it contains whitespace  etc           Decoder decoder   new Decoder flags  new byte len 3 4             if   decoder process input  offset  len  true                 throw new IllegalArgumentException  bad base-64                          Maybe we got lucky and allocated exactly enough output space          if  decoder op    decoder output length                return decoder output                        Need to shorten the array  so allocate a new one of the            right size and copy          byte   temp   new byte decoder op           System arraycopy decoder output  0  temp  0  decoder op           return temp            static class Decoder extends Coder                  private static final int DECODE                   -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  62  -1  -1  -1  63              52  53  54  55  56  57  58  59  60  61  -1  -1  -1  -2  -1  -1              -1   0   1   2   3   4   5   6   7   8   9  10  11  12  13  14              15  16  17  18  19  20  21  22  23  24  25  -1  -1  -1  -1  -1              -1  26  27  28  29  30  31  32  33  34  35  36  37  38  39  40              41  42  43  44  45  46  47  48  49  50  51  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1                                     Decode lookup table for the  web safe  variant  RFC 3548            sec  4  where - and   replace   and                        private static final int DECODE WEBSAFE                   -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  62  -1  -1              52  53  54  55  56  57  58  59  60  61  -1  -1  -1  -2  -1  -1              -1   0   1   2   3   4   5   6   7   8   9  10  11  12  13  14              15  16  17  18  19  20  21  22  23  24  25  -1  -1  -1  -1  63              -1  26  27  28  29  30  31  32  33  34  35  36  37  38  39  40              41  42  43  44  45  46  47  48  49  50  51  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1              -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1                          Non-data values in the DECODE arrays             private static final int SKIP   -1          private static final int EQUALS   -2            private int state       state number  0 to 6          private int value           final private int   alphabet           public Decoder int flags  byte   output                this output   output               alphabet     flags  amp  URL SAFE     0    DECODE   DECODE WEBSAFE              state   0              value   0                      public int maxOutputSize int len                return len   3 4   10                                    Decode another block of input data                         return true if the state machine is still healthy   false if                    bad base-64 data has been detected in the input stream                      public boolean process byte   input  int offset  int len  boolean finish                if  this state    6  return false               int p   offset              len    offset               int state   this state              int value   this value              int op   0              final byte   output   this output              final int   alphabet   this alphabet               while  p  lt  len                                    if  state    0                        while  p 4  lt   len  amp  amp                              value     alphabet input p   amp  0xff   lt  lt  18                                          alphabet input p 1   amp  0xff   lt  lt  12                                          alphabet input p 2   amp  0xff   lt  lt  6                                          alphabet input p 3   amp  0xff      gt   0                            output op 2     byte  value                          output op 1     byte   value  gt  gt  8                           output op     byte   value  gt  gt  16                           op    3                          p    4                                            if  p  gt   len  break                                     int d   alphabet input p     amp  0xff                    switch  state                    case 0                      if  d  gt   0                            value   d                            state                        else if  d    SKIP                            this state   6                          return false                                            break                   case 1                      if  d  gt   0                            value    value  lt  lt  6    d                            state                        else if  d    SKIP                            this state   6                          return false                                            break                   case 2                      if  d  gt   0                            value    value  lt  lt  6    d                            state                        else if  d    EQUALS                               Emit the last  partial  output tuple                             expect exactly one more padding character                          output op       byte   value  gt  gt  4                           state   4                        else if  d    SKIP                            this state   6                          return false                                            break                   case 3                      if  d  gt   0                               Emit the output triple and return to state 0                          value    value  lt  lt  6    d                          output op 2     byte  value                          output op 1     byte   value  gt  gt  8                           output op     byte   value  gt  gt  16                           op    3                          state   0                        else if  d    EQUALS                               Emit the last  partial  output tuple                             expect no further data or padding characters                          output op 1     byte   value  gt  gt  2                           output op     byte   value  gt  gt  10                           op    2                          state   5                        else if  d    SKIP                            this state   6                          return false                                            break                   case 4                      if  d    EQUALS                              state                        else if  d    SKIP                            this state   6                          return false                                            break                   case 5                      if  d    SKIP                            this state   6                          return false                                            break                                               if   finish                       We re out of input  but a future call could provide                    more                  this state   state                  this value   value                  this op   op                  return true                              switch  state                case 0                  break              case 1                  this state   6                  return false              case 2                  output op       byte   value  gt  gt  4                   break              case 3                 output op       byte   value  gt  gt  10                   output op       byte   value  gt  gt  2                   break              case 4                  this state   6                  return false              case 5                  break                             this state   state              this op   op              return true                           --------------------------------------------------------         encoding         --------------------------------------------------------         public static String encodeToString byte   input  int flags            try               return new String encode input  flags    US-ASCII              catch  UnsupportedEncodingException e                   US-ASCII is guaranteed to be available              throw new AssertionError e                         public static String encodeToString byte   input  int offset  int len  int flags            try               return new String encode input  offset  len  flags    US-ASCII              catch  UnsupportedEncodingException e                   US-ASCII is guaranteed to be available              throw new AssertionError e                         public static byte   encode byte   input  int flags            return encode input  0  input length  flags               public static byte   encode byte   input  int offset  int len  int flags            Encoder encoder   new Encoder flags  null               Compute the exact length of the array we will produce          int output len   len   3   4              Account for the tail of the data and the padding bytes  if any          if  encoder do padding                if  len   3  gt  0                    output len    4                          else               switch  len   3                    case 0  break                  case 1  output len    2  break                  case 2  output len    3  break                                      Account for the newlines  if any          if  encoder do newline  amp  amp  len  gt  0                output len       len-1     3   Encoder LINE GROUPS     1                     encoder do cr   2   1                      encoder output   new byte output len           encoder process input  offset  len  true            assert encoder op    output len           return encoder output                package    static class Encoder extends Coder                          Emit a new line every this many output tuples   Corresponds to            a 76-character line length  the maximum allowable according to             lt a href  http   www ietf org rfc rfc2045 txt  gt RFC 2045 lt  a gt                        public static final int LINE GROUPS   19                          Lookup table for turning Base64 alphabet positions  6 bits             into output bytes                      private static final byte ENCODE                    A    B    C    D    E    F    G    H    I    J    K    L    M    N    O    P                Q    R    S    T    U    V    W    X    Y    Z    a    b    c    d    e    f                g    h    i    j    k    l    m    n    o    p    q    r    s    t    u    v                w    x    y    z    0    1    2    3    4    5    6    7    8    9                                                Lookup table for turning Base64 alphabet positions  6 bits             into output bytes                      private static final byte ENCODE WEBSAFE                    A    B    C    D    E    F    G    H    I    J    K    L    M    N    O    P                Q    R    S    T    U    V    W    X    Y    Z    a    b    c    d    e    f                g    h    i    j    k    l    m    n    o    p    q    r    s    t    u    v                w    x    y    z    0    1    2    3    4    5    6    7    8    9    -                            final private byte   tail             package    int tailLen          private int count           final public boolean do padding          final public boolean do newline          final public boolean do cr          final private byte   alphabet           public Encoder int flags  byte   output                this output   output               do padding    flags  amp  NO PADDING     0              do newline    flags  amp  NO WRAP     0              do cr    flags  amp  CRLF     0              alphabet     flags  amp  URL SAFE     0    ENCODE   ENCODE WEBSAFE               tail   new byte 2               tailLen   0               count   do newline   LINE GROUPS   -1                                     return an overestimate for the number of bytes   code            len  bytes could encode to                      public int maxOutputSize int len                return len   8 5   10                     public boolean process byte   input  int offset  int len  boolean finish                   Using local variables makes the encoder about 9  faster              final byte   alphabet   this alphabet              final byte   output   this output              int op   0              int count   this count               int p   offset              len    offset              int v   -1                  First we need to concatenate the tail of the previous call                with any input bytes available now and see if we can empty                the tail               switch  tailLen                    case 0                         There was no tail                      break                   case 1                      if  p 2  lt   len                               A 1-byte tail with at least 2 bytes of                            input available now                          v     tail 0   amp  0xff   lt  lt  16                                  input p     amp  0xff   lt  lt  8                                 input p     amp  0xff                           tailLen   0                                             break                   case 2                      if  p 1  lt   len                               A 2-byte tail with at least 1 byte of input                          v     tail 0   amp  0xff   lt  lt  16                                  tail 1   amp  0xff   lt  lt  8                                 input p     amp  0xff                           tailLen   0                                            break                             if  v    -1                    output op      alphabet  v  gt  gt  18   amp  0x3f                   output op      alphabet  v  gt  gt  12   amp  0x3f                   output op      alphabet  v  gt  gt  6   amp  0x3f                   output op      alphabet v  amp  0x3f                   if  --count    0                        if  do cr  output op        r                       output op        n                       count   LINE GROUPS                                                  At this point either there is no tail  or there are fewer                than 3 bytes of input available                  The main loop  turning 3 input bytes into 4 output bytes on                each iteration              while  p 3  lt   len                    v     input p   amp  0xff   lt  lt  16                          input p 1   amp  0xff   lt  lt  8                         input p 2   amp  0xff                   output op    alphabet  v  gt  gt  18   amp  0x3f                   output op 1    alphabet  v  gt  gt  12   amp  0x3f                   output op 2    alphabet  v  gt  gt  6   amp  0x3f                   output op 3    alphabet v  amp  0x3f                   p    3                  op    4                  if  --count    0                        if  do cr  output op        r                       output op        n                       count   LINE GROUPS                                               if  finish                     if  p-tailLen    len-1                        int t   0                      v     tailLen  gt  0   tail t      input p      amp  0xff   lt  lt  4                      tailLen -  t                      output op      alphabet  v  gt  gt  6   amp  0x3f                       output op      alphabet v  amp  0x3f                       if  do padding                            output op                                   output op                                                     if  do newline                            if  do cr  output op        r                           output op        n                                           else if  p-tailLen    len-2                        int t   0                      v      tailLen  gt  1   tail t      input p      amp  0xff   lt  lt  10                               tailLen  gt  0   tail t      input p      amp  0xff   lt  lt  2                       tailLen -  t                      output op      alphabet  v  gt  gt  12   amp  0x3f                       output op      alphabet  v  gt  gt  6   amp  0x3f                       output op      alphabet v  amp  0x3f                       if  do padding                            output op                                                     if  do newline                            if  do cr  output op        r                           output op        n                                           else if  do newline  amp  amp  op  gt  0  amp  amp  count    LINE GROUPS                        if  do cr  output op        r                       output op        n                                      assert tailLen    0                  assert p    len                else                      Save the leftovers in tail to be consumed on the next                    call to encodeInternal                   if  p    len-1                        tail tailLen      input p                     else if  p    len-2                        tail tailLen      input p                       tail tailLen      input p 1                                                this op   op              this count   count               return true                       private Base64            don t instantiate

User · Answer

No need to use commons--Sun ships a base64 encoder with Java   You can import it as such   import sun misc BASE64Decoder    And then use it like this   BASE64Decoder decoder   new BASE64Decoder    byte   decodedBytes   decoder decodeBuffer encodedBytes     Where encodedBytes is either a java lang String or a java io InputStream   Just beware that the sun   classes are not  officially supported  by Sun   EDIT  Who knew this would be the most controversial answer I d ever post   I do know that sun   packages are not supported or guaranteed to continue existing  and I do know about Commons and use it all the time   However  the poster asked for a class that that was  included with Sun Java 6   and that s what I was trying to answer   I agree that Commons is the best way to go in general   EDIT 2  As amir75 points out below  Java 6  ships with JAXB  which contains supported code to encode decode Base64  Please see Jeremy Ross  answer below

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Given a test encode decode example of javax xml bind DatatypeConverter using methods parseBase64Binary   and printBase64Binary   referring to  jeremy-ross and  nightfirecat answer    Test public void EncodeDecode           ENCODE     String hello    Hello World       byte   helloBytes   hello getBytes StandardCharsets UTF 8       String encodedHello   DatatypeConverter printBase64Binary helloBytes       LOGGER info hello     encoded  gt      encodedHello          DECODE     byte   encodedHelloBytes   DatatypeConverter parseBase64Binary encodedHello       String helloAgain   new String encodedHelloBytes  StandardCharsets UTF 8        LOGGER info encodedHello     decoded  gt      helloAgain        Assert assertEquals hello  helloAgain       Result   INFO - Hello World encoded  gt  SGVsbG8gV29ybGQ  INFO - SGVsbG8gV29ybGQ  decoded  gt  Hello World

[java] Decode Base64 data in Java

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