When working with a programming language, you may want to convert strings to integers. An example would be performing a mathematical operation using the value of a string variable.

In this article, you'll learn how to convert a string to an integer in Java using two methods of the `Integer` class — `parseInt()` and `valueOf()`.

## How to Convert a String to an Integer in Java Using `Integer.parseInt`

The `parseInt()` method takes the string to be converted to an integer as a parameter. That is:

``Integer.parseInt(string_varaible)``

Before looking at an example of its usage, let's see what happens when you add a string value and an integer without any sort of conversion:

``````class StrToInt {
public static void main(String[] args) {
String age = "10";

System.out.println(age + 20);
// 1020
}
}``````

In the code above, we created an `age` variable with a string value of "10".

When added to an integer value of 20, we got 1020 instead of 30.

Here's a quick fix using the `parseInt()` method:

``````class StrToInt {
public static void main(String[] args) {
String age = "10";

int age_to_int = Integer.parseInt(age);

System.out.println(age_to_int + 20);
// 30
}
}``````

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 + 20`.

## How to Convert a String to an Integer in Java Using `Integer.valueOf`

The `valueOf()` methods works just like the `parseInt()` method. It takes the string to be converted to an integer as its parameter.

Here's an example:

``````class StrToInt {
public static void main(String[] args) {
String age = "10";

int age_to_int = Integer.valueOf(age);

System.out.println(age_to_int + 20);
// 30
}
}``````

The explanation for the code above is the same as the last section:

• We passed the string as a parameter to `valueOf()`: `Integer.valueOf(age)`. It was stored in a variable called `age_to_int`.
• We then added 20 to the variable created: `age_to_int + 20`. The resulting value was 30 instead of 1020.

## Summary

We saw how to convert a string to an integer in Java using two methods of the `Integer` class — `parseInt()` and `valueOf()`.