simplemicrobenchmark.java

《Thinking in Java 4th Edition》 Source Code

//: concurrency/SimpleMicroBenchmark.java
// The dangers of microbenchmarking.
import java.util.concurrent.locks.*;

abstract class Incrementable {
  protected long counter = 0;
  public abstract void increment();
}

class SynchronizingTest extends Incrementable {
  public synchronized void increment() { ++counter; }
}

class LockingTest extends Incrementable {
  private Lock lock = new ReentrantLock();
  public void increment() {
    lock.lock();
    try {
      ++counter;
    } finally {
      lock.unlock();
    }
  }
}

public class SimpleMicroBenchmark {
  static long test(Incrementable incr) {
    long start = System.nanoTime();
    for(long i = 0; i < 10000000L; i++)
      incr.increment();
    return System.nanoTime() - start;
  }
  public static void main(String[] args) {
    long synchTime = test(new SynchronizingTest());
    long lockTime = test(new LockingTest());
    System.out.printf("synchronized: %1$10d\n", synchTime);
    System.out.printf("Lock:         %1$10d\n", lockTime);
    System.out.printf("Lock/synchronized = %1$.3f",
      (double)lockTime/(double)synchTime);
  }
} /* Output: (75% match)
synchronized:  244919117
Lock:          939098964
Lock/synchronized = 3.834
*///:~