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  1. import java.util.concurrent.Callable;
  2. import java.util.concurrent.ExecutionException;
  3. import java.util.concurrent.ExecutorService;
  4. import java.util.concurrent.Executors;
  5. import java.util.concurrent.Future;
  6.  
  7.  
  8. class ProcessingChainElement implements Callable<String> {
  9.     private final Future<String> previous;
  10.     public ProcessingChainElement(Future<String> previousResult) {
  11.         previous = previousResult;
  12.     }
  13.     @Override
  14.     public String call() throws Exception {
  15.         // prepare something that may take some time..
  16.         Thread.sleep(500);
  17.         String result;
  18.         if (previous != null) {
  19.             result = previous.get() + " [" + System.currentTimeMillis() + "]";
  20.         } else {
  21.             result = "[" + System.currentTimeMillis() + "]";
  22.         }
  23.         return result;
  24.     }
  25. }
  26.  
  27. public class Main {
  28.  
  29.     public static void main(String[] args) throws InterruptedException, ExecutionException {
  30.         long start = System.currentTimeMillis();
  31.  
  32.         ExecutorService executor = Executors.newFixedThreadPool(3);
  33.         Future<String> result1 = executor.submit(new ProcessingChainElement(null));
  34.         Future<String> result2 = executor.submit(new ProcessingChainElement(result1));
  35.         Future<String> result3 = executor.submit(new ProcessingChainElement(result2));
  36.         executor.shutdown();
  37.  
  38.         logTime("submitting", start);
  39.  
  40.         start = System.currentTimeMillis();
  41.         String result = result3.get();
  42.         logTime("getting result", start);
  43.  
  44.         System.out.println("Result is: " + result);
  45.     }
  46.  
  47.     private static void logTime(String what, long start) {
  48.         long end = System.currentTimeMillis();
  49.         long diff = end - start;
  50.         System.out.printf("[%s] took %4d ms%n", what, diff);
  51.     }
  52. }
  53.  
Success #stdin #stdout 0.08s 382336KB
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stdin
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Standard input is empty
stdout
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[submitting] took    4 ms
[getting result] took  495 ms
Result is: [1375710427753] [1375710427753] [1375710427754]
https://ideone.com/VAg8q3
language:
Java (HotSpot 12)
created:
12 years ago
visibility:
secret

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