Extract digits from a string in Java

Question

I have a Java String object  I need to extract only digits from it  I ll give an example    123-456-789  I want  123456789   Is there a library function that extracts only digits   Thanks for the answers  Before I try these I need to know if I have to install any additional llibraries

User · Answer

I inspired by code Sean Patrick Floyd and little rewrite it for maximum performance i get.

public static String stripNonDigitsV2( CharSequence input ) {
    if (input == null)
        return null;
    if ( input.length() == 0 )
        return "";

    char[] result = new char[input.length()];
    int cursor = 0;
    CharBuffer buffer = CharBuffer.wrap( input );

    while ( buffer.hasRemaining() ) {
        char chr = buffer.get();
        if ( chr > 47 && chr < 58 )
            result[cursor++] = chr;
    }

    return new String( result, 0, cursor );
}

i do Performance test to very long String with minimal numbers and result is:

Original code is 25,5% slower
Guava approach is 2.5-3 times slower
Regular expression with D+ is 3-3.5 times slower
Regular expression with only D is 25+ times slower

Btw it depends on how long that string is. With string that contains only 6 number is guava 50% slower and regexp 1 times slower

User · Answer

Use regular expression to match your requirement   String num num1 num2  String str    123-456-789   String regex      d     Matcher matcher   Pattern compile  regex   matcher  str   while  matcher find       num   matcher group         System out print num

User · Answer

Here s a more verbose solution  Less elegant  but probably faster   public static String stripNonDigits              final CharSequence input    inspired by seh s comment          final StringBuilder sb   new StringBuilder              input length      also inspired by seh s comment          for int i   0  i  lt  input length    i             final char c   input charAt i           if c  gt  47  amp  amp  c  lt  58               sb append c                       return sb toString        Test Code   public static void main final String   args       final String input    0-123-abc-456-xyz-789       final String result   stripNonDigits input       System out println result       Output      0123456789   BTW  I did not use Character isDigit ch  because it accepts many other chars except 0 - 9

User · Answer

You can use regex and delete non-digits   str   str replaceAll    D

User · Answer

input replaceAll    0-9              This will ignore the decimal points   eg  if you have an input as 445 3kg the output will be 445 3

User · Answer

I have finalized the code for phone numbers  9  987  124124   Unicode characters occupy 4 bytes   public static String stripNonDigitsV2  CharSequence input         if  input    null          return null      if   input length      0           return          char   result   new char input length         int cursor   0      CharBuffer buffer   CharBuffer wrap  input        int i 0      while   i lt  buffer length          buffer hasRemaining           char chr   buffer get i           if  chr   u                i i 5              chr buffer get i                      if   chr  gt  39  amp  amp  chr  lt  58               result cursor      chr          i i 1             return new String  result  0  cursor

User · Answer

Using Google Guava   CharMatcher DIGIT retainFrom  123-456-789      CharMatcher is plug-able and quite interesting to use  for instance you can do the following   String input    My phone number is 123-456-789    String output   CharMatcher is  -   or CharMatcher DIGIT  retainFrom input     output    123-456-789

User · Answer

Using Google Guava   CharMatcher inRange  0   9   retainFrom  123-456-789     UPDATE   Using Precomputed CharMatcher can further improve performance  CharMatcher ASCII DIGITS CharMatcher inRange  0   9   precomputed      ASCII DIGITS retainFrom  123-456-789

User · Answer

Using Kotlin and Lambda expressions you can do it like this  val digitStr   str filter   it isDigit

User · Answer

public String extractDigits String src        StringBuilder builder   new StringBuilder        for  int i   0  i  lt  src length    i              char c   src charAt i           if  Character isDigit c                 builder append c                       return builder toString

User · Answer

Code   public class saasa        public static void main String   args               TODO Auto-generated method stub         String t  123-456-789           t t replaceAll  -                System out println t

User · Answer

import java util    public class FindDigits    public static void main String   args       FindDigits h new  FindDigits        h checkStringIsNumerical         void checkStringIsNumerical        String h  hello 123 for the rest of the 98475wt355        for int i 0 i lt h length   i             if h charAt i                System out println  Is this    h charAt i     is a digit    Character isDigit h charAt i                        void checkStringIsNumerical2        String h  hello 123 for 2the rest of the 98475wt355        for int i 0 i lt h length   i                char chr h charAt i         if chr               if Character isDigit chr              System out print chr

User · Answer

public class FindDigitFromString         public static void main String   args                 String s    Hi How Are You 11                     String s1 s replaceAll    0-9                     replacing all the value of string except digit by using    0-9    regex          System out println s1                      Output  11

User · Answer

You can use str replaceAll    0-9

[java] Extract digits from a string in Java

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