//TestLock.java
package com.test.thread;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
public class TestLock {
private static int cnt=0;
private final int num=cnt++;
private static Lock lock=new ReentrantLock();
private TestLock(){}
private static TestLock ins=null;
public static /*synchronized */ TestLock getInstance(){
if(ins==null){
//若在此处声明锁，则不能保证多个线程访问时，此段代码的安全
//Lock lock=new ReentrantLock();
lock.lock();
try {
if (ins== null) {
TimeUnit.MILLISECONDS.sleep(10);
ins = new TestLock();
}
} catch (InterruptedException e) {
e.printStackTrace();
}
finally{
lock.unlock();
}
}
return ins;
}
public int getNum() {
return num;
}
/**
* @param args
*/
public static void main(String[] args) {
ExecutorService svs = Executors.newCachedThreadPool();
List< Future<TestLock> > lstObjs=new ArrayList< Future<TestLock> >();
for (int i = 0;i<10;i++){
lstObjs.add( svs.submit(new TestLockThread()) );
}
for (Future<TestLock> ftl : lstObjs) {
try {
TestLock tl= ftl.get();
} catch (InterruptedException e) {
e.printStackTrace();
} catch (ExecutionException e) {
e.printStackTrace();
}
}
svs.shutdown();
}
}
//TestLockThread.java
package com.test.thread;
import java.util.concurrent.Callable;
public class TestLockThread implements Callable<TestLock> {
@Override
public TestLock call() throws Exception {
TestLock tl = TestLock.getInstance();
System.out.println("call:"+tl.getNum());
return tl;
}
}
