Question

How to check if a string contains only digits in Java

Answer 1

import java.util.regex.Pattern;
 
public class StringContainsOnlyDigits_Java {
    public static void main(String args[]) {
        Pattern pattern = Pattern.compile(".*[^0-9].*");
        
        String s = "3762724";
        System.out.println(!pattern.matcher(s).matches());
 
        s = "3762724W";
        System.out.println(!pattern.matcher(s).matches());
         
        pattern = Pattern.compile(".*\\D.*");
         
        s = "83947592384";
        System.out.println(!pattern.matcher(s).matches());
    }
}
 
 
 
/*
run:
 
true
false
true
 
*/

 

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Answer 2

public class StringContainsOnlyDigits_Java {
    public static void main(String args[]) {
        String str = "12345";
         
        boolean b = str.matches("\\d+"); 
  
        System.out.println(b);
    }
}
 
 
 
/*
run:
 
true
 
*/

 

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Answer 3

public class StringContainsOnlyDigits_Java {
    public static void main(String args[]) {
        String str = "12345";
         
        boolean b = str.chars().allMatch(Character::isDigit);
  
        System.out.println(b);
    }
}
 
 
 
/*
run:
 
true
 
*/

 

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