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  1. /* package whatever; // don't place package name! */
  2.  
  3. import java.util.*;
  4. import java.util.concurrent.CopyOnWriteArrayList;
  5. import java.util.concurrent.ExecutorService;
  6. import java.util.concurrent.Executors;
  7. import java.util.function.Consumer;
  8.  
  9. class Ideone
  10. {
  11.     private static final Random RANDOM = new Random();
  12.     public static void main(String[] args) {
  13. /*
  14.     Service A   01          03        1
  15.     Service B   02          03        2
  16.     Service C   03          04        3
  17.     Service D   04          05        4
  18.     Service E   05          07        5
  19.     Service F   06          07        6
  20.     Service G   07          (null)    7*/
  21.         CallManager manager = new CallManager();
  22.         manager.addService(simpleRunnable("A"), "A");
  23.         manager.addService(simpleRunnable("B"), "B");
  24.         manager.addService(simpleRunnable("C"), "C", "A", "B");
  25.         manager.addService(simpleRunnable("D"), "D", "C");
  26.         manager.addService(simpleRunnable("E"), "E", "D");
  27.         manager.addService(simpleRunnable("F"), "F");
  28.         manager.addService(simpleRunnable("G"), "G", "E", "F");
  29.  
  30.         manager.run();
  31.     }
  32.  
  33.     // create some simple pseudo service
  34.     private static Runnable simpleRunnable(String s) {
  35.         return () -> {
  36.             System.out.printf("running service %s%n", s);
  37.             try {
  38.                 Thread.sleep(RANDOM.nextInt(2000));
  39.             } catch (InterruptedException e) {
  40.                 e.printStackTrace();
  41.             }
  42.         };
  43.     }
  44. }
  45.  
  46. class CallManager {
  47.     List<Service> services = new ArrayList<>();
  48.     ExecutorService executorService = Executors.newFixedThreadPool(4);
  49.  
  50.     void addService(Runnable r, String serviceName, String... preconditions) {
  51.         services.add(new Service(r, serviceName, this::preconditionFulfilled, preconditions));
  52.     }
  53.  
  54.     void run() {
  55.         for (Iterator<Service> serviceIterator = services.iterator(); serviceIterator.hasNext(); ) {
  56.             Service service = serviceIterator.next();
  57.             if (service.arePreconditionsFulfilled()) {
  58.                 executorService.submit(service);
  59.                 serviceIterator.remove();
  60.             }
  61.             if (services.isEmpty()) {
  62.                 executorService.shutdown();
  63.             }
  64.         }
  65.     }
  66.  
  67.     private synchronized void preconditionFulfilled(String name) {
  68.         System.out.printf("service %s finished%n", name);
  69.         for (Iterator<Service> serviceIterator = services.iterator(); serviceIterator.hasNext(); ) {
  70.             Service service = serviceIterator.next();
  71.             service.preconditionFulfilled(name);
  72.             if (service.arePreconditionsFulfilled()) {
  73.                 executorService.submit(service);
  74.                 serviceIterator.remove();
  75.             }
  76.         }
  77.         if (services.isEmpty()) {
  78.             executorService.shutdown();
  79.         }
  80.     }
  81. }
  82.  
  83. class Service implements Runnable {
  84.  
  85.     private final Runnable wrappedRunnable;
  86.     private final String name;
  87.     private final List<String> preconditions = new CopyOnWriteArrayList<>();
  88.     private final Consumer<String> finishedNotification;
  89.  
  90.     Service(Runnable r, String name, Consumer<String> finishedNotification, String... preconditions) {
  91.         this.wrappedRunnable = r;
  92.         this.name = name;
  93.         this.finishedNotification = finishedNotification;
  94.         this.preconditions.addAll(Arrays.asList(preconditions));
  95.     }
  96.  
  97.     @Override
  98.     public void run() {
  99.         wrappedRunnable.run();
  100.         finishedNotification.accept(name);
  101.     }
  102.  
  103.     void preconditionFulfilled(String precondition) {
  104.         preconditions.remove(precondition);
  105.     }
  106.     boolean arePreconditionsFulfilled() {
  107.         return preconditions.isEmpty();
  108.     }
  109. }
Success #stdin #stdout 0.14s 34908KB
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Standard input is empty
stdout
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running service A
running service B
running service F
service A finished
service F finished
service B finished
running service C
service C finished
running service D
service D finished
running service E
service E finished
running service G
service G finished
https://ideone.com/a7Awla
language:
Java (HotSpot 12)
created:
5 years ago
visibility:
public

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