AtomicReference weakCompareAndSet() method in Java with Examples

The weakCompareAndSet() method of a AtomicReference class is used to atomically sets the value to newValue for AtomicReference if the current value is equal to expectedValue passed as parameter. This method update the value with memory semantics of reading as if the variable was declared volatile type of variable. This method returns true if set a new value to AtomicReference is successful.

Syntax:

public final boolean weakCompareAndSet(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 true if successful.

Below programs illustrate the weakCompareAndSet() method:
Program 1:



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// Java program to demonstrate
// AtomicReference.weakCompareAndSet() method
  
import java.util.concurrent.atomic.AtomicReference;
  
public class GFG {
    public static void main(String[] args)
    {
  
        // create an atomic reference object
        // which stores Integer.
        AtomicReference<Integer> ref
            = new AtomicReference<Integer>();
  
        // set some value
        ref.set(999);
  
        // apply weakCompareAndSet()
        boolean result
            = ref.weakCompareAndSet(999,
                                    999999);
  
        // print value
        System.out.println("Setting new value"
                           + " is successful = "
                           + result);
        System.out.println("New Value = "
                           + ref.get());
    }
}

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Output:

Setting new value is successful = false
New Value = 999

Program 2:

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// Java program to demonstrate
// AtomicReference.weakCompareAndSet() method
  
import java.util.concurrent.atomic.AtomicReference;
  
public class GFG {
    public static void main(String[] args)
    {
  
        // create an atomic reference object
        // which stores String.
        AtomicReference<String> ref
            = new AtomicReference<String>();
  
        // set some value
        ref.set("GEEKS FOR GEEKS");
  
        // apply weakCompareAndSet()
        ref.weakCompareAndSet("GEEKS FOR GEEKS",
                              "GFG");
  
        // print value
        System.out.println("Value  = "
                           + ref.get());
    }
}

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Output:

Value  = GFG

References: https://docs.oracle.com/javase/10/docs/api/java/util/concurrent/atomic/AtomicReference.html#weakCompareAndSet(V, V)

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