import java.util.concurrent.*; public class ForkJoinExample { public static void print(double[] array) { for (int i = 0; i < array.length; i++) System.out.println(array[i] + " "); System.out.println(); } public static void main(String[] args) { double[] array = new double [100]; for (int i = 0; i < array.length; i++) array[i] = Math.random() * array.length; print(array); ParallelSquareRoot psr = new ParallelSquareRoot(0, array.length, array); psr.invoke(); System.out.println(); print(array); } } public class ParallelSquareRoot extends RecursiveAction { int start; int end; int thresholdSize = 10; double[] array; public ParallelSquareRoot(int start, int end, double[] array) { this.start = start; this.end = end; this.array = array; } @Override public void compute() { if (end < start) return; if ((end - start) < thresholdSize) { for (int i = start; i < end; i++) array[i] = Math.sqrt(array[i]); return; } int mid = (start + end) >> 1; invokeAll(new ParallelSquareRoot(start, mid, array), new ParallelSquareRoot(mid, end, array)); } }