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  1. import java.util.logging.*;
  2.  
  3. public class Main {
  4.     public static final LicenseManager licenseManager = new LicenseManager();
  5.  
  6.     static class LicenseManager {
  7.         private static final Logger logger =
  8.                 Logger.getLogger(LicenseManager.class.getName());
  9.  
  10.         class InsufficientApplesException extends RuntimeException {};
  11.         class InsufficientPiesException extends RuntimeException {};
  12.  
  13.         private int apples = 10;
  14.         private int pies = 10;
  15.         private boolean enterpriseLoggingEnabled = true;
  16.  
  17.         // Apples have high contention; so they get their own lock.
  18.         private final Object appleLock = new Object();
  19.  
  20.         void useApple() {
  21.             checkExpired();
  22.             synchronized (appleLock) {
  23.                 logger.info("Using apple. Apples left: " + apples + ". " + Thread.currentThread());
  24.                 if (apples == 0) throw new InsufficientApplesException();
  25.                 apples--;
  26.             }
  27.         }
  28.  
  29.         /* Examples. There are lots of other operations like this
  30.          * on LicenseManager. We don't have time to prove that
  31.          * they are commutative, so we just use the main object lock
  32.          * around them all. The exception is when we find one with high
  33.          * contention, for example apples. */
  34.         synchronized void usePear() {checkExpired(); /*...*/}
  35.         synchronized void checkExpired() {}
  36.  
  37.         synchronized void usePie() {
  38.             checkExpired();
  39.             logger.info("Using pie. Pies left: " + pies + ". " + Thread.currentThread());
  40.             if (pies == 0) throw new InsufficientPiesException();
  41.             boolean reallyCanUsePie = true; // do expensive pie computation
  42.             if (reallyCanUsePie) {
  43.                 useApple(); /* using a pie requires an apple.
  44.                              * TODO: stop putting apples in the pumpkin pie */
  45.                 pies--;
  46.             }
  47.         }
  48.  
  49.         synchronized boolean isEnterpriseLoggingEnabled() {
  50.             return enterpriseLoggingEnabled;
  51.         }
  52.     }
  53.  
  54.     public static void main(String[] args) {
  55.         // Install enterprise log handler on the root logger
  56.         Logger.getLogger("").addHandler(new Handler() {
  57.             @Override
  58.             public void publish(LogRecord lr) {
  59.                 System.out.println("TEST." + lr.getMessage() + ". " + Thread.currentThread());
  60.                 if (licenseManager.isEnterpriseLoggingEnabled())
  61.                     System.out.println("ENTERPRISE ALERT! [" 
  62.                             + lr.getLevel() + "] " + lr.getMessage() + ". " + Thread.currentThread());
  63.             }
  64.             @Override public void flush() {}
  65.             @Override public void close() throws SecurityException {}
  66.         });
  67.  
  68.         // Simulate fat user
  69.         new Thread() {
  70.             @Override
  71.             public void run() {
  72.                 while (true) {
  73.                     licenseManager.usePie();
  74.                 }
  75.             }
  76.         }.start();
  77.  
  78.         // Simulate fat albeit healthy user
  79.         while (true) {
  80.             licenseManager.useApple();
  81.         }
  82.     }
  83. }
  84.  
Time limit exceeded #stdin #stdout 5s 381312KB
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TEST.Using apple. Apples left: 10. Thread[main,5,main]. Thread[main,5,main]
TEST.Using pie. Pies left: 10. Thread[Thread-1,5,main]. Thread[Thread-1,5,main]
ENTERPRISE ALERT! [INFO] Using pie. Pies left: 10. Thread[Thread-1,5,main]. Thread[Thread-1,5,main]
https://ideone.com/Z6Dqgr
language:
Java (HotSpot 12)
created:
12 years ago
visibility:
public

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