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。

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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();
    }
}
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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