Question

How to determine if a String is an Integer in Java

Answer 1

public class MyClass {
    public static boolean isInteger(String str) {
        for (int i = 0; i < str.length(); i++) {
            if (!Character.isDigit(str.charAt(i))) {
                return false;
            }
        }
        return true;
    }
     
    public static void main(String args[]) {
        String str = "9674830";
    
        System.out.println(isInteger(str));
    }
}
  
  
  
  
/*
run:
   
true
   
*/

 

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Answer 2

public class MyClass {
    public static boolean isInteger(String str) {
        try {
            Integer.parseInt(str);
            return true;
        } catch (NumberFormatException e) {
            return false;
        }
    }
     
    public static void main(String args[]) {
        String str = "9674830";
    
        System.out.println(isInteger(str));
    }
}
  
  
  
/*
run:
   
true
   
*/

 

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Answer 3

public class MyClass {
    public static boolean isInteger(String str) {
        return str.matches("^-?\\d+$");
    }
    
    public static void main(String args[]) {
        String str = "9674830";
   
        System.out.println(isInteger(str));
    }
}
 
 
 
/*
run:
  
true
  
*/

 

70+ SQL courses for beginners and professionals