ThreadTest.java：
package main;
import java.util.concurrent.atomic.AtomicLong;
import net.jcip.annotations.GuardedBy;
import net.jcip.annotations.ThreadSafe;
@ThreadSafe
public class ThreadTest {
private long hits1;
@GuardedBy("this")
private long hits2;
private final AtomicLong count = new AtomicLong(0);
public long getCounts() {
return count.get();
}
public synchronized long getHits1() {
return hits1;
}
public synchronized long getHits2() {
return hits2;
}
public synchronized void IncreaseHits1() {
++hits1;
}
public void service(int n) throws InterruptedException {
for (int i = 1; i <= n; i++) {
new Thread(new Runnable() {
@Override
public void run() {
// TODO Auto-generated method stub
synchronized (this) {
++hits2;
}
IncreaseHits1();
count.incrementAndGet();
}
}).start();
}
System.err.println("All Threads running!");
Thread.currentThread().sleep(2000);
System.out.println("hits1:" + getHits1() + " hits2:" + getHits2()
+ " AtomicLong:" + getCounts());
}
}main.java:
package main;
public class main {
public static void main(String[] args) throws InterruptedException {
ThreadTest threadTest = new ThreadTest();
for (int i = 0; i < 1000; i++) {
threadTest.service(10000);
}
}
}請問，hits2是否最後的結果是否正確，是否線程安全？
當累計跑了185次service後，控制檯輸出爲：
synchronized (this) {
++hits2;
}看輸出結果的話，上面這這一小段同步塊代碼貌似並非是線程安全的。不瞭解java註解有什麼作用如@ThreadSafe和@GuardedBy("this")，應該不會對運行結果造成什麼影響吧。