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  1. /* package whatever; // don't place package name! */
  2. import java.util.Random; 
  3. import java.util.concurrent.ForkJoinPool; 
  4. import java.util.concurrent.RecursiveTask; 
  5.  
  6. public class MaximumFinder extends RecursiveTask<Integer> { 
  7.  
  8.   private static final int SEQUENTIAL_THRESHOLD = 5; 
  9.  
  10.   private final int[] data; 
  11.   private final int start; 
  12.   private final int end; 
  13.  
  14.   public MaximumFinder(int[] data, int start, int end) { 
  15.     this.data = data; 
  16.     this.start = start; 
  17.     this.end = end; 
  18.   } 
  19.  
  20.   public MaximumFinder(int[] data) { 
  21.     this(data, 0, data.length); 
  22.   } 
  23.  
  24.   @Override
  25.   protected Integer compute() { 
  26.     final int length = end - start; 
  27.     if (length < SEQUENTIAL_THRESHOLD) { 
  28.       return computeDirectly(); 
  29.     } 
  30.     final int split = length / 2; 
  31.     final MaximumFinder left = new MaximumFinder(data, start, start + split); 
  32.     left.fork(); 
  33.     final MaximumFinder right = new MaximumFinder(data, start + split, end); 
  34.     return Math.max(right.compute(), left.join()); 
  35.   } 
  36.  
  37.   private Integer computeDirectly() { 
  38.     System.out.println(Thread.currentThread() + " computing: " + start 
  39.                        + " to " + end); 
  40.     int max = Integer.MIN_VALUE; 
  41.     for (int i = start; i < end; i++) { 
  42.       if (data[i] > max) { 
  43.         max = data[i]; 
  44.       } 
  45.     } 
  46.     return max; 
  47.   } 
  48.  
  49.   public static void main(String[] args) { 
  50.     // create a random data set 
  51.     final int[] data = new int[1000]; 
  52.     final Random random = new Random(); 
  53.     for (int i = 0; i < data.length; i++) { 
  54.       data[i] = random.nextInt(100); 
  55.     } 
  56.  
  57.     // submit the task to the pool 
  58.     final ForkJoinPool pool = new ForkJoinPool(4); 
  59.     final MaximumFinder finder = new MaximumFinder(data); 
  60.     System.out.println(pool.invoke(finder)); 
  61.   } 
  62. }
  63.  
Compilation error #stdin compilation error #stdout 0s 0KB
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stdin
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Standard input is empty
compilation info 
Main.java:6: error: class MaximumFinder is public, should be declared in a file named MaximumFinder.java
public class MaximumFinder extends RecursiveTask<Integer> { 
       ^
1 error
stdout
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Standard output is empty
https://ideone.com/nDjAco
language:
Java (12.0.1)
created:
9 years ago
visibility:
public

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