Forum libero

Scritto da: ::1
> http://stackoverflow.com/a/6123354

public class SynchroTest {
	
	public static class StopWatch {
		public long start = System.currentTimeMillis(), stop = -1;
		public void stop() {
			stop = System.currentTimeMillis();
		}
		public void reset() {
			start = System.currentTimeMillis();
			stop = -1;
		}
		public String toString() {
			return (stop - start) + "ms";
		}
	}
	
	public static void main(String[] args) throws Exception {
		System.out.println(System.getProperty("java.fullversion"));
		int N = 1000000;
		StopWatch s = new StopWatch();
		StringBuffer sb = new StringBuffer(N);
		s.reset();
		for (int i=0;i<N;i++) {
			sb.append('a');
		}
		s.stop();
		System.out.println("append non synchronized: "+s);
		sb = new StringBuffer(N);
		s.reset();
		synchronized(sb) {
			for (int i=0;i<N;i++) {
				sb.append('a');
			}
		}
		s.stop();
		System.out.println("append synchronized: "+s);
	}
}

J2RE 1.5.0 IBM J9 2.3 Windows XP x86-32 j9vmwi3223-20111020 (JIT enabled)
J9VM - 20111017_92807_lHdSMr
JIT  - 20110916_20782_r8
GC   - 20110524_AA
append non synchronized: 47ms
append synchronized: 93ms