Left padding a String with Zeros

Question

I ve seen similar questions here and here   But am not getting how to left pad a String with Zero   input   129018  output   0000129018   The total output length should be TEN

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Use Google Guava   Maven    lt dependency gt        lt artifactId gt guava lt  artifactId gt        lt groupId gt com google guava lt  groupId gt        lt version gt 14 0 1 lt  version gt   lt  dependency gt    Sample code   Strings padStart  129018   10   0   returns  0000129018

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To format String use   import org apache commons lang StringUtils   public class test        public static void main String   args             String result   StringUtils leftPad  wrwer   10   0            System out println  The String       result              Output   The String   00000wrwer  Where the first argument is the string to be formatted  Second argument is the length of the desired output length and third argument is the char with which the string is to be padded   Use the link to download the jar http   commons apache org proper commons-lang download lang cgi

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Based on  Haroldo Mac  do s answer  I created a method in my custom Utils class such as         Left padding a string with the given character        param str     The string to be padded     param length  The total fix length of the string     param padChar The pad character     return The padded string     public static String padLeft String str  int length  String padChar        String pad           for  int i   0  i  lt  length  i              pad    padChar            return pad substring str length      str      Then call Utils padLeft str  10   0

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I prefer this code   public final class StrMgr        public static String rightPad String input  int length  String fill                              String pad   input trim     String format     length  s       replace      fill           return pad substring 0  length                                   public static String leftPad String input  int length  String fill                       String pad   String format     length  s       replace      fill    input trim            return pad substring pad length   - length  pad length               and then   System out println StrMgr leftPad  hello   20   x      System out println StrMgr rightPad  hello   20   x

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Here s another approach   int pad   4  char   temp    new String new char pad      129018   toCharArray   Arrays fill temp  0  pad   0    System out println temp

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String str    129018   String str2   String format   10s   str  replace       0    System out println str2

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String str    129018   StringBuilder sb   new StringBuilder     for  int toPrepend 10-str length    toPrepend gt 0  toPrepend--        sb append  0       sb append str   String result   sb toString

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If your string contains numbers only  you can make it an integer and then do padding   String format   010d   Integer parseInt mystring      If not I would like to know how it can be done

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Check my code that will work for integer and String   Assume our first number is 129018  And we want to add zeros to that so the the length of final string will be 10  For that you can use following code      int number 129018      int requiredLengthAfterPadding 10      String resultString Integer toString number       int inputStringLengh resultString length        int diff requiredLengthAfterPadding-inputStringLengh      if inputStringLengh lt requiredLengthAfterPadding                resultString new String new char diff   replace   0    0   number                    System out println resultString

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I have used this   DecimalFormat numFormat   new DecimalFormat  00000    System out println  Code format    numFormat format 123      Result  00123  I hope you find it useful

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Here is a solution based on String format that will work for strings and is suitable for variable length   public static String PadLeft String stringToPad  int padToLength       String retValue   null      if stringToPad length    lt  padToLength            retValue   String format   0    String valueOf padToLength - stringToPad length       d s  0 stringToPad             else          retValue   stringToPad            return retValue     public static void main String   args        System out println       PadLeft  test   10              System out println       PadLeft  test   3              System out println       PadLeft  test   4              System out println       PadLeft  test   5              Output   000000test   test   test   0test

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This will pad left any string to a total width of 10 without worrying about parse errors     String unpadded    12345    String padded                substring unpadded length      unpadded     unpadded is  12345    padded   is       12345    If you want to pad right   String unpadded    12345    String padded   unpadded                substring unpadded length        unpadded is  12345    padded   is  12345           You can replace the     characters with whatever character you would like to pad with  repeated the amount of times that you want the total width of the string to be  E g  if you want to add zeros to the left so that the whole string is 15 characters long     String unpadded    12345    String padded    000000000000000  substring unpadded length      unpadded     unpadded is  12345    padded   is  000000000012345      The benefit of this over khachik s answer is that this does not use Integer parseInt  which can throw an Exception  for example  if the number you want to pad is too large like 12147483647   The disadvantage is that if what you re padding is already an int  then you ll have to convert it to a String and back  which is undesirable      So  if you know for sure that it s an int  khachik s answer works great  If not  then this is a possible strategy

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String paddedString   org apache commons lang StringUtils leftPad  129018   10   0     the second parameter is the desired output length   0  is the padding char

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An old question  but I also have two methods       For a fixed  predefined  length         public static String fill String text            if  text length    gt   10              return text          else             return  0000000000  substring text length      text            For a variable length         public static String fill String text  int size            StringBuilder builder   new StringBuilder text           while  builder length    lt  size                builder append  0                      return builder toString

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The solution by Satish is very good among the expected answers  I wanted to make it more general by adding variable n to format string instead of 10 chars   int maxDigits   10  String str    129018   String formatString       n  s   String str2   String format formatString  str  replace       0    System out println str2     This will work in most situations

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You may use apache commons StringUtils  StringUtils leftPad  129018   10   0      https   commons apache org proper commons-lang javadocs api-2 6 org apache commons lang StringUtils html leftPad java lang String  20int  20char

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int number   -1      int holdingDigits   7      System out println String format   0   holdingDigits   d   number      Just asked this in an interview          My answer below but this  mentioned above  is much nicer-   String format   05d   num    My answer is   static String leadingZeros int num  int digitSize          test for capacity being too small       if  digitSize  lt  String valueOf num  length              return  Error   you number      num     is higher than the decimal system specified capacity of     digitSize     zeros               test for capacity will exactly hold the number        else if  digitSize    String valueOf num  length              return String valueOf num              else do something here to calculate if the digitSize will over flow the StringBuilder buffer java lang OutOfMemoryError             else calculate and return string       else           StringBuilder sb   new StringBuilder            for  int i   0  i  lt  digitSize  i                  sb append  0                      sb append String valueOf num            return sb substring sb length   - digitSize  sb length

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Here s my solution   String s   Integer toBinaryString 5     Convert decimal to binary int p   8    preferred length for int g 0 j s length   g lt p-j g    s   0    s   System out println s     Output  00000101

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Right padding with fix length-10  String format   1 -10s    abc   Left padding with fix length-10  String format   1 10s    abc

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If you need performance and know the maximum size of the string use this   String zeroPad    0000000000000000   String str0   zeroPad substring str length      str    Be aware of the maximum string size  If it is bigger then the StringBuffer size  you ll get a java lang StringIndexOutOfBoundsException

[java] Left padding a String with Zeros

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