AtomicReferenceArray weakCompareAndSet() method in Java with Examples

Last Updated : 3 Jan, 2020
The weakCompareAndSet() method of a AtomicReferenceArray class is used to atomically sets the value of the element at index i to newValue to newValue for AtomicReferenceArray if the current value is equal to expectedValue passed as parameter. This method updates the value at index i 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(
           int i, E expectedValue, E newValue)
Parameters: This method accepts:
  • i which is an index of AtomicReferenceArray to perform the operation,
  • expectedValue which is the expected value and
  • newValue which is the new value to set.
Return value: This method returns true if set a new value to AtomicReference is successful. Below programs illustrate the weakCompareAndSet() method: Program 1: Java 
// Java program to demonstrate
// weakCompareAndSet() method

import java.util.concurrent.atomic.*;

public class GFG {

    public static void main(String[] args)
    {

        // create an atomic reference object.
        AtomicReferenceArray<Integer> ref
            = new AtomicReferenceArray<Integer>(5);

        // set some value
        ref.set(0, 543);
        ref.set(1, 124);
        ref.set(2, 322);

        // apply weakCompareAndSet()
        boolean result
            = ref.weakCompareAndSet(0, 124,
                                    234);

        // print value
        System.out.println("Setting new value"
                           + " is successful = "
                           + result);

        System.out.println("Value of index 0 = "
                           + ref.get(0));
    }
}
Output: 
Setting new value is successful = false
Value of index 0 = 543
Program 2: Java 
// Java program to demonstrate
// weakCompareAndSet() method

import java.util.concurrent.atomic.*;

public class GFG {

    public static void main(String[] args)
    {

        // create an atomic reference object.c
        AtomicReferenceArray<String> ref
            = new AtomicReferenceArray<String>(5);

        // set some value
        ref.set(0, "INDIA");
        ref.set(1, "US");
        ref.set(2, "UK");
        ref.set(3, "CHINA");
        ref.set(4, "CHINA");

        // apply weakCompareAndSet()
        boolean result
            = ref.weakCompareAndSet(4, "CHINA",
                                    "CANADA");

        // print value
        System.out.println("Setting new value"
                           + " is successful = "
                           + result);

        System.out.println("Value of index 4 = "
                           + ref.get(4));
    }
}
Output: 
Setting new value is successful = true
Value of index 4 = CANADA
References: https://docs.oracle.com/javase/10/docs/api/java/util/concurrent/atomic/AtomicReferenceArray.html#weakCompareAndSet(V, V)
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