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  1. import java.util.ArrayList;
  2. import java.util.List;
  3. import java.util.concurrent.*;
  4. import java.util.concurrent.atomic.AtomicBoolean;
  5.  
  6. public class Main {
  7.  
  8.     public static void main(String[] args) throws Exception {
  9.         AtomicBoolean processing = new AtomicBoolean(true);
  10.  
  11.         new Executor.Builder()
  12.                 .add(() -> {
  13.                     System.out.println("TASK 1 Start");
  14.                     try {
  15.                         Thread.sleep(2000);
  16.                     } catch (InterruptedException e) {
  17.                         e.printStackTrace();
  18.                     }
  19.                     System.out.println("TASK 1 Complete");
  20.                 })
  21.                 .add(() -> {
  22.                     System.out.println("TASK 2 Start");
  23.                     try {
  24.                         Thread.sleep(500);
  25.                     } catch (InterruptedException e) {
  26.                         e.printStackTrace();
  27.                     }
  28.                     System.out.println("TASK 2 Complete");
  29.                 })
  30.                 .add(() -> {
  31.                     System.out.println("TASK 3 Start");
  32.                     try {
  33.                         Thread.sleep(1000);
  34.                     } catch (InterruptedException e) {
  35.                         e.printStackTrace();
  36.                     }
  37.                     System.out.println("TASK 3 Complete");
  38.                 })
  39.                 .callback(() -> {
  40.                     System.out.println("All TASK COMPLETED");
  41.                     processing.set(false);
  42.                 })
  43.                 .build()
  44.                 .execute();
  45.  
  46.         while (processing.get()) {
  47.             // program runs continuously
  48.         }
  49.         System.out.println("Program Terminates");
  50.     }
  51.  
  52.     public static class Executor extends Thread {
  53.         private ConcurrentLinkedQueue<Worker> workers;
  54.         private Callback callback;
  55.         private CountDownLatch latch;
  56.  
  57.         private Executor(List<Runnable> tasks, Callback callback) {
  58.             super();
  59.             this.callback = callback;
  60.             workers = new ConcurrentLinkedQueue<>();
  61.             latch = new CountDownLatch(tasks.size());
  62.  
  63.             for (Runnable task : tasks) {
  64.                 workers.add(new Worker(task, latch));
  65.             }
  66.         }
  67.  
  68.         public void execute() {
  69.             start();
  70.         }
  71.  
  72.         @Override
  73.         public void run() {
  74.             while (true) {
  75.                 Worker worker = workers.poll();
  76.                 if (worker == null) {
  77.                     break;
  78.                 }
  79.                 worker.start();
  80.             }
  81.  
  82.             try {
  83.                 latch.await();
  84.             } catch (InterruptedException e) {
  85.                 e.printStackTrace();
  86.             }
  87.  
  88.             if (callback != null) {
  89.                 callback.onComplete();
  90.             }
  91.         }
  92.  
  93.         public static class Builder {
  94.             private List<Runnable> tasks = new ArrayList<>();
  95.             private Callback callback;
  96.  
  97.             public Builder add(Runnable task) {
  98.                 tasks.add(task);
  99.                 return this;
  100.             }
  101.  
  102.             public Builder callback(Callback callback) {
  103.                 this.callback = callback;
  104.                 return this;
  105.             }
  106.  
  107.             public Executor build() {
  108.                 return new Executor(tasks, callback);
  109.             }
  110.         }
  111.  
  112.         public interface Callback {
  113.             void onComplete();
  114.         }
  115.     }
  116.  
  117.     public static class Worker implements Runnable {
  118.  
  119.         private AtomicBoolean started;
  120.         private Runnable task;
  121.         private Thread thread;
  122.         private CountDownLatch latch;
  123.  
  124.         public Worker(Runnable task, CountDownLatch latch) {
  125.             this.latch = latch;
  126.             this.task = task;
  127.             started = new AtomicBoolean(false);
  128.             thread = new Thread(this);
  129.         }
  130.  
  131.         public void start() {
  132.             if (!started.getAndSet(true)) {
  133.                 thread.start();
  134.             }
  135.         }
  136.  
  137.         @Override
  138.         public void run() {
  139.             task.run();
  140.             latch.countDown();
  141.         }
  142.     }
  143. }
Success #stdin #stdout 2.19s 2446336KB
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stdin
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Standard input is empty
stdout
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TASK 1 Start
TASK 2 Start
TASK 3 Start
TASK 2 Complete
TASK 3 Complete
TASK 1 Complete
All TASK COMPLETED
Program Terminates
https://ideone.com/RuWabo
language:
Java (HotSpot 12)
created:
6 years ago
visibility:
public

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