Java AtomicInteger compareAndSet() method

The compareAndSet() method of Java AtomicInteger class compares the current value with the expected value. If both the values are same, it will update the value.

Syntax

Parameter

expect: It is the expected value

update: It is the new value

Return

This method returns the new value as an atomicInteger if the expected value is equal to the current value.

Example 1

import java.util.concurrent.atomic.AtomicInteger;
public class AtomicIntegerCompareAndSetExample1 
{
    public static void main(String[] args) 
    {
        AtomicInteger number = new AtomicInteger(222);
        int expectedValue = 222;
        int newValue = 444;
        number.compareAndSet(expectedValue, newValue);
        System.out.println("the updated number: " + number);
    }
}

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Output:

the updated number: 444

Example 2

import java.util.concurrent.atomic.AtomicInteger;
public class AtomicIntegerCompareAndSetExample2
{
    public static void main(String[] args) 
    {
        AtomicInteger number = new AtomicInteger(222);
        int expectedValue = 223;
        int newValue = 444;
        number.compareAndSet(expectedValue, newValue);
        System.out.println("the updated number:"+number);
    }
}

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Output:

the updated number:222

In the above example, the expected value is not equal to the newValue so, the value is not updated and it remains as intial value.

Example 3

import java.util.concurrent.atomic.AtomicInteger;
public class AtomicIntegerCompareAndSetExample3 
{
    public static void main(String[] args) 
    {
        AtomicInteger number = new AtomicInteger(-222);
        int expectedValue = -222;
        int newValue = 0;
        number.compareAndSet(expectedValue, newValue);
        System.out.println("the updated number: " + number);
    }
}

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Output:

the updated number: 0

Example 4

import java.util.concurrent.atomic.AtomicInteger;
public class AtomicIntegerCompareAndSetExample4 
{
    public static void main(String[] args) 
    {
        AtomicInteger number = new AtomicInteger();
        int expectedValue = 0;
        int newValue = 100;
        number.compareAndSet(expectedValue, newValue);
        System.out.println("the updated number: " + number);
    }
}

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Output:

the updated number: 100

Example 5

import java.util.concurrent.atomic.AtomicInteger;
public class AtomicIntegerCompareAndSetExample5 
{
    public static void main(String[] args) 
    {
        AtomicInteger number = new AtomicInteger(-2);
        int expectedValue = 1;
        int newValue = 10;
        number.compareAndSet(expectedValue, newValue);
        System.out.println("the updated number: " + number);
    }
}

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Output: