Java Utility Library

Java Arrays - parallelPrefix() Method

The java.util.Arrays.parallelPrefix() method is used to cumulate, in parallel, each element of the given array in place, using the supplied function. For example if the array initially holds [2, 1, 0, 3] and the operation performs addition, then upon return the array holds [2, 3, 3, 6].

Syntax

public static <T> void parallelPrefix(T[] array, 
                                      BinaryOperator<T> op)

Here, T is the type of elements in the array.

Parameters

`array`	Specify the array, which is modified in-place by this method.
`op`	Specify a side-effect-free, associative function to perform the cumulation.

Return Value

void type.

Exception

Throws NullPointerException, if the specified array or function is null.

Example:

In the example below, the java.util.Arrays.parallelPrefix() method is used to add, in parallel, each element of the given array in place.

import java.util.*;

public class MyClass {
  
  //Adds two Long numbers 
  static Long MyFunc(Long x, Long y) { 
    return x + y; 
  } 

  public static void main(String[] args) {
    //creating a Long array
    Long[] Arr = {1L, 2L, 3L, 4L, 5L};

    //printing Arr
    System.out.print("Arr contains:"); 
    for(Long i: Arr)
      System.out.print(" " + i);
      
    //MyFunc is used with parallelPrefix method
    //to add each elements of the array 
    Arrays.parallelPrefix(Arr, (a,b) -> MyFunc(a,b));

    //printing Arr
    System.out.print("\nArr contains:"); 
    for(Long i: Arr)
      System.out.print(" " + i);
  }
}

The output of the above code will be:

Arr contains: 1 2 3 4 5
Arr contains: 1 3 6 10 15

❮ Java.util - Arrays