java的同步方法和同步代码块，对象锁，类锁区别

大家好，又见面了，我是全栈君。

/**
 * @author admin
 * @date 2018/1/12 9:48
 * 作用在同一个实例对象上讨论
 * synchronized同步方法的测试
 * 两个线程，一个线程调用synchronized修饰方法，另一个线程可以调用非synchronized修饰的方法，互不影响
 */
public class SynchronizedTest {

    public synchronized void methodA() {
        try {
            for (int i = 0; i < 5; i++) {
                System.out.println("methodA-" + i);
                Thread.sleep(1000);
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    public void methodB() {
        try {
            for (int i = 0; i < 5; i++) {
                System.out.println("methodB-" + i );
                Thread.sleep(1000);
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

    }

    public static void main(String[] args) {
        SynchronizedTest test = new SynchronizedTest();
        Thread thread1 = new Thread(new Runnable() {
            @Override
            public void run() {
                test.methodA();
            }
        });
        thread1.start();

        Thread thread2 = new Thread(new Runnable() {
            @Override
            public void run() {
                test.methodB();
            }
        });
        thread2.start();
    }
}

运行结果：
methodA-0
methodB-0
methodA-1
methodB-1
methodB-2
methodA-2
methodA-3
methodB-3
methodA-4
methodB-4

/**
 * @author admin
 * @date 2018/1/12 10:16
 * 作用在同一个实例对象上讨论
 * Sychronized代码块的测试
 * 两个线程，一个线程执行synchronized代码块，另一个线程执行非synchronized代码块
 */
public class SychronizedTest2 {
    public void methodA() {
        synchronized (this) {
            try {
                for (int i = 0; i < 5; i++) {
                    System.out.println("methodA-" + i);
                    Thread.sleep(1000);
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }

        }
    }

    public void methodB() {
        try {
            for (int i = 0; i < 5; i++) {
                System.out.println("methodB-" + i);
                Thread.sleep(1000);
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        SychronizedTest2 test2 = new SychronizedTest2();
        Thread thread1 = new Thread(new Runnable() {
            @Override
            public void run() {
               test2.methodA();
            }
        });
        thread1.start();

        Thread thread2 = new Thread(new Runnable() {
            @Override
            public void run() {
                test2.methodB();
            }
        });
        thread2.start();
    }
}

运行结果：
methodA-0
methodB-0
methodA-1
methodB-1
methodA-2
methodB-2
methodB-3
methodA-3
methodA-4
methodB-4

/**
 * @author admin
 * @date 2018/1/12 10:33
 * 作用在同一个实例对象上讨论
 * Synchronized同步方法和同步代码块
 * 1、synchronized和synchronized（this）二者没区别，都作用在this对象锁上面，所以会同步
 * 2、synchronized（obj），这个是作用在obj对象锁上面，和this对象锁不同，所以不会同步
 */
public class SynchronizedTest3 {
    public synchronized void methodA() {
        try {
            for (int i = 0; i < 5; i++) {
                System.out.println("methodA-" + i);
                Thread.sleep(1000);
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    public void methodB() {
        synchronized (this) {
            try {
                for (int i = 0; i < 5; i++) {
                    System.out.println("methodB-" + i);
                    Thread.sleep(1000);
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

    public void methodC() {
        Object obj = new Object();
        synchronized (obj) {
            try {
                for (int i = 0; i < 5; i++) {
                    System.out.println("methodC-" + i);
                    Thread.sleep(1000);
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

    public static void main(String[] args) {
        SynchronizedTest3 test3 = new SynchronizedTest3();
        Thread thread1 = new Thread(new Runnable() {
            @Override
            public void run() {
                test3.methodA();
            }
        });
        thread1.start();

        Thread thread2 = new Thread(new Runnable() {
            @Override
            public void run() {
                test3.methodB();
            }
        });
        thread2.start();

        Thread thread3 = new Thread(new Runnable() {
            @Override
            public void run() {
                test3.methodC();
            }
        });
        thread3.start();

    }
}

运行结果：
methodA-0
methodC-0
methodA-1
methodC-1
methodA-2
methodC-2
methodA-3
methodC-3
methodA-4
methodC-4
methodB-0
methodB-1
methodB-2
methodB-3
methodB-4

/**
 * @author admin
 * @date 2018/1/12 10:48
 * 作用在同一个类上讨论，每一个类只有一个类锁
 * synchronized类锁
 * static synchronized 和 synchronized（SynchronizedTest4.class）,都是作用在同一个类锁上，所以会同步
 */
public class SynchronizedTest4 {
    public synchronized static void methodA() {
        try {
            for (int i = 0; i < 5; i++) {
                System.out.println("methodA-" + i);
                Thread.sleep(1000);
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    public void methodB() {
        synchronized (SynchronizedTest4.class) {
            try {
                for (int i = 0; i < 5; i++) {
                    System.out.println("methodB-" + i);
                    Thread.sleep(1000);
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

    public static void main(String[] args) {
        SynchronizedTest4 test4 = new SynchronizedTest4();
        Thread thread1 = new Thread(new Runnable() {
            @Override
            public void run() {
                test4.methodA();
            }
        });
        thread1.start();

        Thread thread2 = new Thread(new Runnable() {
            @Override
            public void run() {
                test4.methodB();
            }
        });
        thread2.start();
    }
}

运行结果：
methodA-0
methodA-1
methodA-2
methodA-3
methodA-4
methodB-0
methodB-1
methodB-2
methodB-3
methodB-4

/**
 * @author admin
 * @date 2018/1/12 11:03
 * synchronized的对象锁和static synchronized的类锁，是两个不同的锁，所以不会同步
 * 两个线程，一个调用对象锁，一个调用类锁
 */
public class SynchronizedTest5 {
    public synchronized  void methodA() {
        try {
            for (int i = 0; i < 5; i++) {
                System.out.println("methodA-" + i);
                Thread.sleep(1000);
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    public synchronized static void methodB() {
        try {
            for (int i = 0; i < 5; i++) {
                System.out.println("methodB-" + i);
                Thread.sleep(1000);
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        SynchronizedTest5 test5 = new SynchronizedTest5();
        Thread thread1 = new Thread(new Runnable() {
            @Override
            public void run() {
                test5.methodA();
            }
        });
        thread1.start();

        Thread thread2 = new Thread(new Runnable() {
            @Override
            public void run() {
                test5.methodB();
            }
        });
        thread2.start();
    }
}

运行结果：
methodA-0
methodB-0
methodA-1
methodB-1
methodB-2
methodA-2
methodB-3
methodA-3
methodB-4
methodA-4

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