How to Convert a String to an Integer in Java?

The parseInt() method is used to convert the string to an integer as a parameter. That is:

Integer.parseInt(string_varaible)

Let us see what will happened while we add a string value and an integer without any sort of conversion:

class Test {

    public static void main(String[] args) {

        String age = "30";

        

        System.out.println(age + 30);

        // 3030

    }

}

In the above example, we created an age variable with a string value of "30".

While added to an integer value of 30, we got 3030 instead of 60.

Here's a solution using the parseInt() method:

class Test {

    public static void main(String[] args) {

        String age = "30";

        

        int age_to_int = Integer.parseInt(age);

        

        System.out.println(age_to_int + 30);

        // 60

    }

}

In order to convert the age variable to an integer, we passed it as a parameter to the parseInt() method — Integer.parseInt(age) — and stored it in a variable called age_to_int.

When added to another integer, we got a proper addition: age_to_int + 30.