Java program converts string (string) type variable to int

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In this program, we will learn how to convert a String type variable to an integer (int) in Java.

To understand this example, you should understand the followingJava ProgrammingTopic:

• Java Variables and (Primitive) Data Types

• Java String

Example1: Java program that uses parseInt() to convert string to int

class Main {
　　public static void main(String[] args) {
　　　　//Create a string variable
　　　　String str1　"23";
　　　　String str2　"4566";
　　　　//Convert string to int
　　　　//use parseInt()
　　　　int num1　= Integer.parseInt(str1);
　　　　int num2　= Integer.parseInt(str2);
　　　　//Print int value
　　　　System.out.println(num1);　　　　//　23
　　　　System.out.println(num2);　　　　//　4566
　　}
}

In the above example, we used the parseInt() method of the Integer class to convert a string variable to an int.

Here, Integer is a wrapper class in Java. For more information, please visitJava Wrapper Class.

Note: A string variable should represent an int value. Otherwise, the compiler will throw an exception. For example,

class Main {
　　public static void main(String[] args) {
　　　　//Create a string variable
　　　　String str1　= "w3codebox";
　　　　//Convert string to int
　　　　//use parseInt()
　　　　int num1　= Integer.parseInt(str1);
　　　　//Print int value
　　　　System.out.println(num1);　　　　//　throws an exception NumberFormatException
　　}
}

Example2: Java program uses valueOf() to convert string to int

We can also use the valueOf() method to convert a string variable to an Integer object. For example,

class Main {
　　public static void main(String[] args) {
　　　　//Create a string variable
　　　　String str1　"643";
　　　　String str2　"1312";
　　　　//Convert string to int
　　　　//Using valueOf()
　　　　int num1　Integer.valueOf(str1);
　　　　int num2　Integer.valueOf(str2);
　　　　//　Print int value
　　　　System.out.println(num1);　　　　//　643
　　　　System.out.println(num2);　　　　//　1312
　　}
}

In the above example, the valueOf () method of the Integer class converts the string variable to int.

In this case, the valueOf () method actually returns an Integer object of the class. However, the object is automatically converted to the primitive type. This is called unboxing in Java. For more information, please visitJava Auto-boxing and Unboxing.

That is,

//　valueOf() returns an Integer object
//　Object to int conversion
int num1　Integer obj = Integer.valueOf(str1)

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