静态工具方法并发时候不能简单的用同步关键字来同步方法，因为静态方法是类级别的方法，锁定的是这个类class本身，这样的结果就是任何一个同步的静态方法运行，都会导致其他同步方法调用的阻塞。这个也是问题所在。
这里给出一个简单的方法来避免这个问题：
通过给每个方法一个锁来控制并发，就可以巧妙的解决阻塞问题。
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
/**
* 静态工具方法的并发控制
*
* @author leizhimin 2014/7/19 17:18
*/
public class Test {
private static final Lock lock1 = new ReentrantLock();
private static final Lock lock2 = new ReentrantLock();
public static void t1() throws InterruptedException {
lock1.lock();
System.out.println(Thread.currentThread().getName() + ": t1...");
Thread.sleep(500L);
lock1.unlock();
}
public static void t2() throws InterruptedException {
lock2.lock();
System.out.println(Thread.currentThread().getName() + ": t2...");
lock2.unlock();
}
public static void main(String[] args) {
new Thread(new Runnable() {
@Override
public void run() {
try {
t1();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}).start();
new Thread(new Runnable() {
@Override
public void run() {
try {
t1();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}).start();
new Thread(new Runnable() {
@Override
public void run() {
try {
t1();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}).start();
new Thread(new Runnable() {
@Override
public void run() {
try {
t2();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}).start();
new Thread(new Runnable() {
@Override
public void run() {
try {
t2();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}).start();
new Thread(new Runnable() {
@Override
public void run() {
try {
t2();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}).start();
}
}D:\jdk1.7.0_55\bin\java 。。。 Thread-0: t1... Thread-3: t2... Thread-4: t2... Thread-5: t2... Thread-2: t1... Thread-1: t1... Process finished with exit code 0
