Java Integer valueOf() example

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In this guide, you will learn about the Integer valueOf() method in Java programming and how to use it with an example.

1. Integer valueOf() Method Overview

Definition:

The valueOf() method of the Java Integer class returns an Integer object holding the value of the specified int or string.

Syntax:

1. Integer.valueOf(int i)
2. Integer.valueOf(String s)
3. Integer.valueOf(String s, int radix)

Parameters:

int i: The primitive integer value to be converted to an Integer object.

String s: The string to be parsed into an Integer object.

int radix: The base of the numeral system used in the string (only relevant for the third syntax, default is 10).

Key Points:

- The method provides a way to obtain Integer objects without using the new keyword.

- The valueOf() method is often used for boxing, i.e., converting a primitive int to an Integer object.

- If the string does not contain a parsable integer, a NumberFormatException will be thrown.

- The method is static, which means it's called on the class (Integer) rather than on an instance of the class.

2. Integer valueOf() Method Example

public class ValueOfExample {
    public static void main(String[] args) {
        // Convert primitive int to Integer object
        int num = 100;
        Integer intObject = Integer.valueOf(num);
        System.out.println("Integer object from int: " + intObject);

        // Convert String to Integer object
        String numberStr = "200";
        Integer intFromString = Integer.valueOf(numberStr);
        System.out.println("Integer object from string: " + intFromString);

        // Convert String in hexadecimal (base 16) to Integer object
        String hexStr = "1a";
        Integer intFromHex = Integer.valueOf(hexStr, 16);
        System.out.println("Integer object from hex string: " + intFromHex);
    }
}

Output:

Integer object from int: 100
Integer object from string: 200
Integer object from hex string: 26

Explanation:

In the example, we started by converting a primitive integer value (100) to an Integer object using the valueOf() method. 

We then parsed a string "200" to get its Integer representation. 

Lastly, we demonstrated the use of the radix parameter by parsing a hexadecimal string "1a" (which is 26 in base 10) into an Integer object.

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