多个线程多个锁

/**
 * 关键字synchronized取得的锁都是对象锁！！！！！而不是把一段代码（方法）当做锁，
 * 所以代码中哪个线程先执行synchronized关键字的方法，哪个线程就持有该方法所属对象的锁（Lock），
 * 在静态方法上加synchronized关键字，表示锁定.class类，类一级别的锁（独占.class类）。
 */
public class MultiThread {
    private int num = 0;
    public synchronized void printNum(String tag){
        try {
            if(tag.equals("a")){
                num = 100;
                System.out.println("tag a, set num over!");
                Thread.sleep(1000);
            } else {
                num = 200;
                System.out.println("tag b, set num over!");
            }
            System.out.println("tag " + tag + ", num = " + num);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
    //注意观察run方法输出顺序
    public static void main(String[] args) {
        //俩个不同的对象
        final MultiThread m1 = new MultiThread();
        final MultiThread m2 = new MultiThread();
        Thread t1 = new Thread(new Runnable() {
            @Override
            public void run() {
                m1.printNum("a");
            }
        });
        Thread t2 = new Thread(new Runnable() {
            @Override 
            public void run() {
                m2.printNum("b");
            }
        });        
        t1.start();
        t2.start();
    }
}
/**
 * 输出：tag a, set num over!
        tag b, set num over!
        tag b, num = 200
        tag a, num = 100
 */

/**
 * 关键字synchronized取得的锁都是对象锁！！！！！而不是把一段代码（方法）当做锁，
 * 所以代码中哪个线程先执行synchronized关键字的方法，哪个线程就持有该方法所属对象的锁（Lock），
 * 在静态方法上加synchronized关键字，表示锁定.class类，类一级别的锁（独占.class类）。
 */
public class MultiThread {
    private static int num = 0;
    public synchronized static void printNum(String tag){
        try {
            if(tag.equals("a")){
                num = 100;
                System.out.println("tag a, set num over!");
                Thread.sleep(1000);
            } else {
                num = 200;
                System.out.println("tag b, set num over!");
            }
            System.out.println("tag " + tag + ", num = " + num);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
    //注意观察run方法输出顺序
    public static void main(String[] args) {
        //俩个不同的对象
        final MultiThread m1 = new MultiThread();
        final MultiThread m2 = new MultiThread();
        Thread t1 = new Thread(new Runnable() {
            @Override
            public void run() {
                m1.printNum("a");
            }
        });
        Thread t2 = new Thread(new Runnable() {
            @Override 
            public void run() {
                m2.printNum("b");
            }
        });        
        t1.start();
        t2.start();
    }
}
/**
 * 输出：tag a, set num over!
        tag a, num = 100
        tag b, set num over!
        tag b, num = 200
 */