AtomicLongArray accumulateAndGet() method in Java with Examples

The Java.util.concurrent.atomic.AtomicLongArray.accumulateAndGet() is an inbuilt method in java that atomically updates the element at index i with the results of applying the given function to the current and given values, returning the updated value. The function should be side-effect-free, since it may be re-applied when attempted updates fail due to contention among threads. The function is applied with the current value at index i as its first argument, and the given update as the second argument.

Syntax:

public final long accumulateAndGet(int i, long x, LongBinaryOperator accumulatorFunction)



Parameters: The function accepts three parameters:

  • i – The index where update is to be mada.
  • x – The value to make operation with value at i
  • accumulatorFunction – A side-effect-free function of two arguments.
  • Return value: The function returns the updated value which is in long.

    Below programs illustrate the above method:
    Program 1:

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    // Java program that demonstrates
    // the accumulateAndGet() function
      
    import java.util.concurrent.atomic.AtomicLongArray;
    import java.util.function.LongBinaryOperator;
      
    public class GFG {
        public static void main(String args[])
        {
            // Initializing an array
            long a[] = { 1, 2, 3, 4, 5 };
      
            // Initializing an AtomicLongArray with array a
            AtomicLongArray arr = new AtomicLongArray(a);
      
            // Displaying the AtomicLongArray
            System.out.println("The array : " + arr);
      
            // Index where update is to be made
            int idx = 4;
      
            // Value to make operation with value at idx
            long x = 5;
      
            // Declaring the accumulatorFunction
            LongBinaryOperator add = (u, v) -> u + v;
      
            // Updating the value at idx
            // applying accumulatorFunction
            arr.accumulateAndGet(idx, x, add);
      
            // Displaying the AtomicLongArray
            System.out.println("The array after update : "
                               + arr);
        }
    }

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    Output:

    The array : [1, 2, 3, 4, 5]
    The array after update : [1, 2, 3, 4, 10]
    

    Program 2:

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    // Java program that demonstrates
    // the accumulateAndGet() function
      
    import java.util.concurrent.atomic.AtomicLongArray;
    import java.util.function.LongBinaryOperator;
      
    public class GFG {
        public static void main(String args[])
        {
            // Initializing an array
            long a[] = { 17, 22, 33, 44, 55 };
      
            // Initializing an AtomicLongArray with array a
            AtomicLongArray arr = new AtomicLongArray(a);
      
            // Displaying the AtomicLongArray
            System.out.println("The array : " + arr);
      
            // Index where update is to be made
            int idx = 0;
      
            // Value to make operation with value at idx
            long x = 6;
      
            // Declaring the accumulatorFunction
            LongBinaryOperator sub = (u, v) -> u - v;
      
            // Updating the value at idx
            // applying accumulatorFunction
            arr.accumulateAndGet(idx, x, sub);
      
            // Displaying the AtomicLongArray
            System.out.println("The array after update : "
                               + arr);
        }
    }

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    Output:

    The array : [17, 22, 33, 44, 55]
    The array after update : [11, 22, 33, 44, 55]
    

    Reference:
    https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/atomic/AtomicLongArray.html#accumulateAndGet-int-long-java.util.function.LongBinaryOperator-



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