我有两个单例类的实现
public class Test2 {
private static Test2 _instance=new Test2();
private Test2(){
}
public static synchronized Test2 getInstance(){
if(_instance == null){
_instance = new Test2();
}
return _instance;
}
}
和：
public class TestSingleton {
private static TestSingleton _instance=new TestSingleton();
private TestSingleton(){
}
public static TestSingleton getInstance(){
if (_instance == null) {
synchronized (TestSingleton.class) {
if (_instance == null) {
_instance = new TestSingleton();
}
}
}
return _instance;
}
我想根据所花费的时间参数化我的发现，我所做的是：
Callable<Long> task = new Callable<Long>() {
@Override
public Long call() throws Exception {
long start = System.nanoTime();
**TestSingleton.getInstance();**
long end = System.nanoTime();
return end - start;
}
};
for (int i = 0; i < 100000; i++) {
futList.add(es1.submit(task));
}
for (Future<Long> fut : futList) {
try {
totalTime1.getAndAdd(fut.get());
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (ExecutionException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
System.out.println("Time taken by S1 " + totalTime1.get());
.
.
ExecutorService es2 = Executors.newFixedThreadPool(threadpool);
Callable<Long> task1 = new Callable<Long>() {
@Override
public Long call() throws Exception {
long start = System.nanoTime();
Test2.getInstance();
long end = System.nanoTime();
return end - start;
}
};
for (int i = 0; i < 100000; i++) {
futList1.add(es2.submit(task1));
}
for (Future<Long> fut : futList1) {
try {
totalTime2.getAndAdd(fut.get());
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (ExecutionException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
System.out.println("Time taken by S2 " + totalTime2.get());
我得到的结果是：
S1 4636498 所用时间 S2 5127865 所用时间
第一个问题这是正确的方法吗？其次，即使我getinstances在这两个中注释该方法call()，我也会得到两个相同块的不同执行时间：
S1 所用时间 1506640 S2 2156172 所用时间