Java AtomicBoolean Example
May 11, 2022
AtomicBoolean class.
1. Java
AtomicBoolean is a boolean value that may be updated atomically.
2. The
AtomicBoolean is used in the application where we need atomically updated flags. We should use it in the application when we have multiple threads accessing a boolean variable.
3. The
AtomicBoolean variable is lock-free and thread-safe. Instances of AtomicBoolean maintain values that are accessed and updated using its methods.
4. The
AtomicBoolean should not be used as the replacement of Boolean.
5. The
AtomicBoolean is introduced since Java 5.
6. In our example, we will discuss
getAndSet and compareAndSet methods of AtomicBoolean class.
Creating Instance
The instances ofAtomicBoolean can be created in two ways.
1. With initial default value as false.
AtomicBoolean ab = new AtomicBoolean();
AtomicBoolean(boolean initialValue)
AtomicBoolean ab = new AtomicBoolean(true);
Example-1: getAndSet
Find thegetAndSet declaration from Java doc.
final boolean getAndSet(boolean newValue)
Find the example.
GetAndSetDemo.java
package com.concretepage;
import java.util.concurrent.atomic.AtomicBoolean;
public class GetAndSetDemo {
public static void main(String[] args) {
AtomicBoolean ab1 = new AtomicBoolean(true);
boolean oldVal1 = ab1.getAndSet(false);
System.out.println(ab1.get()); //false
System.out.println(oldVal1); //true
AtomicBoolean ab2 = new AtomicBoolean(false);
boolean oldVal2 = ab2.getAndSet(true);
System.out.println(ab2.get()); //true
System.out.println(oldVal2); //false
}
}
Example-2: Using compareAndSet()
Find thecompareAndSet declaration from Java doc.
final boolean compareAndSet(boolean expectedValue, boolean newValue)
The method returns true if successful.
Find the example.
CompareAndSetDemo.java
package com.concretepage;
import java.util.concurrent.atomic.AtomicBoolean;
public class CompareAndSetDemo {
public static void main(String[] args) {
AtomicBoolean ab = new AtomicBoolean(true);
System.out.println(ab.get()); //true
boolean isSuccess = ab.compareAndSet(false, false); //(current value != expectedValue)
System.out.println(isSuccess); //false
System.out.println(ab.get()); //true (Value not changed)
isSuccess = ab.compareAndSet(true, false); // current value == expectedValue
System.out.println(isSuccess); //true
System.out.println(ab.get()); //false (Value changed)
}
}
Example-3
In this example, we will useAtomicBoolean with multi-threads.
WithMultiThreads.java
package com.concretepage;
import java.util.concurrent.atomic.AtomicBoolean;
public class WithMultiThreads {
AtomicBoolean ab = new AtomicBoolean(true);
class A implements Runnable {
@Override
public void run() {
ab.compareAndSet(false, true);
System.out.println(ab.get());
}
}
class B implements Runnable {
@Override
public void run() {
ab.compareAndSet(true, false);
System.out.println(ab.get());
}
}
public static void main(String... args) {
WithMultiThreads ob = new WithMultiThreads();
new Thread(ob.new A()).start();
new Thread(ob.new B()).start();
}
}
