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The getAndSet() method of a AtomicReferenceArray class is used to atomically sets the value of index i of AtomicReferenceArray object to newValue which is passed as parameter and returns the old value of the AtomicReferenceArray object, with memory effects as specified by VarHandle.getAndSet(java.lang.Object...).VarHandle.getAndSet(java.lang.Object...) specified that variable is handle as memory semantics of setting as if the variable was declared volatile.

Syntax:

public final E getAndSet(int i, E newValue)

Parameters: This method accepts:

i which is an index of AtomicReferenceArray to perform the operation,
newValue which is the new value to set.

Return value: This method returns the old value of index i.
Below programs illustrate the getAndSet() method:
Program 1:

Java

// Java program to demonstrate
// AtomicReferenceArray.getAndSet() 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>(3);

        // set some value
        ref.set(0, 1234);
        ref.set(1, 4322);

        // apply getAndSet()
        int oldV1 = ref.getAndSet(0, 8913);
        int oldV2 = ref.getAndSet(1, 6543);

        // print
        System.out.println("Old value at index 0: "
                           + oldV1);
        System.out.println("New value at index 0: "
                           + ref.get(0));
        System.out.println("Old value at index 1: "
                           + oldV2);
        System.out.println("New value at index 1: "
                           + ref.get(1));
    }
}

Output:

Old value at index 0: 1234
New value at index 0: 8913
Old value at index 1: 4322
New value at index 1: 6543

Program 2:

Java

// Java program to demonstrate
// AtomicReferenceArray.getAndSet() method

import java.util.concurrent.atomic.*;

public class GFG {
    public static void main(String[] args)
    {
        // create an atomic reference object.
        AtomicReferenceArray<String> ref
            = new AtomicReferenceArray<String>(3);

        // set some value
        ref.set(0, "GFG");
        ref.set(1, "JS");

        // apply getAndSet()
        String oldV1
            = ref.getAndSet(0, "GEEKS FOR GEEKS");
        String oldV2
            = ref.getAndSet(1, "JAVA SCRIPT");

        // print
        System.out.println(
            "Old value at index 0: "
            + oldV1);
        System.out.println(
            "New value at index 0: "
            + ref.get(0));
        System.out.println(
            "Old value at index 1: "
            + oldV2);
        System.out.println(
            "New value at index 1: "
            + ref.get(1));
    }
}

Output:

Old value at index 0: GFG
New value at index 0: GEEKS FOR GEEKS
Old value at index 1: JS
New value at index 1: JAVA SCRIPT

References: https://docs.oracle.com/javase/10/docs/api/java/util/concurrent/atomic/AtomicReferenceArray.html#getAndSet(int, E)

AtomicReferenceArray getAndSet() method in Java with Examples

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