AtomicReference compareAndExchange() method in Java with Examples
Last Updated :
27 Dec, 2019
The compareAndExchange() method of a AtomicReference class is used to Atomically sets the value to newValue to AtomicReference object, if the current value of AtomicReference object which is referred to as the witness value is equal to the expectedValue.This method will return the witness value, which will be the same as the expected value. This method handles the operation with memory semantics of reading as if the variable was declared volatile.
Syntax:
public final V compareAndExchange(V expectedValue,
V newValue)
Parameters: This method accepts expectedValue which is the expected value and newValue which is the new value to set.
Return value: This method returns the witness value, which will be the same as the expected value if successful.
Below programs illustrate the compareAndExchange() method:
Program 1:
import java.util.concurrent.atomic.AtomicReference;
public class GFG {
public static void main(String[] args)
{
AtomicReference<Integer> ref
= new AtomicReference<Integer>();
ref.set( 999 );
Integer oldValue
= ref.compareAndExchange(
999 ,
999999 );
System.out.println( "Witness Value= "
+ oldValue);
}
}
|
Output:
Program 2:
import java.util.concurrent.atomic.AtomicReference;
public class GFG {
public static void main(String[] args)
{
AtomicReference<String> ref
ref.set( "GFG" );
String oldValue
= ref.compareAndExchange(
"GFG" ,
"Geeks for Geeks" );
System.out.println( "Witness Value= "
+ oldValue);
}
}
|
Output:
References: https://docs.oracle.com/javase/10/docs/api/java/util/concurrent/atomic/AtomicReference.html#compareAndExchange(V, V)
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