String to int in Java

Last Updated : 22 Nov, 2024
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Converting a String to an int in Java can be done using methods provided in the Integer class, such as Integer.parseInt() or Integer.valueOf() methods.

Example:

The most common method to convert a string to a primitive int is Integer.parseInt(). It throws a NumberFormatException if the string contains non-numeric characters.

Java 
// Java Program to demonstrate 
// String to int conversion using parseInt()
public class StringToInt {
    public static void main(String[] args) {
      
        String s = "12345"; 

        // Convert the string to an integer 
        // using Integer.parseInt()
        int n = Integer.parseInt(s);

        System.out.println("" + n);
    }
}

Output
12345

Other Ways to Convert String to int

Using Integer.valueOf() Method

The Integer.valueOf() method converts a String to an Integer object instead of a primitive int. We can unbox it to an int.

Note: valueOf() method uses parseInt() internally to convert to integer. 

Example:

Java 
// Java ProgramConvert String to int 
// using Integer.valueOf() Method
public class StringToInt { 
  
    public static void main(String[] args) {
      
        // Convert String to Integer using valueOf()
        String s = "217";
      
        // Convert the string to an Integer object 
        // using Integer.valueOf()
        int n = Integer.valueOf(s);
        
        System.out.println("" + n);
    }
}

Output
217


Handling Errors for Non-Numeric Strings

If a string literal does not contain numeric values, calling the Integer.parseInt() or Integer.valueOf() methods will result in a NumberFormatException.

Example:

Java 
// Java Program to Demonstrate Working of parseInt() Method
// where NumberFormatException is Thrown
public class StringToIntExample {

    public static void main(String[] args) {
        
        // NumberFormatException due to empty string
        String s1 = "";
        int n1 = Integer.parseInt(s1); 
        
        // NumberFormatException due to non-numeric string
        String s2 = "geeksforgeeks";
        int n2 = Integer.parseInt(s2); 

        System.out.println(n1);
        System.out.println(n2);
    }
}

Output:

Exception in thread "main" java.lang.NumberFormatException: For input string: ""
	at java.base/java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
	at java.base/java.lang.Integer.parseInt(Integer.java:662)
	at java.base/java.lang.Integer.parseInt(Integer.java:770)
	at StringToIntExample.main(StringToIntExample.java:10)

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