synchronized关键字最主要有以下3种应用方式

修饰实例方法，作用于当前实例加锁，进入同步代码前要获得当前实例的锁；实例锁，一个实例一把锁

修饰静态方法，作用于当前类对象加锁，进入同步代码前要获得当前类对象的锁；对象锁，一个对象一把锁

修饰代码块，指定加锁对象，对给定对象加锁，进入同步代码库前要获得给定对象的锁；对象锁，一个对象一把锁

实例锁public class SuperHakceTest implements Runnable{    public static Integer flag = 0;    public synchronized void instanse(){        flag ++;    }    @Override    public void run() {        for(int i = 0;i < 1000;i ++){            instanse();        }    }    public static void main(String[] args) throws Exception{        SuperHakceTest superHakceTest = new SuperHakceTest();        Thread thread1 = new Thread(superHakceTest);        Thread thread2 = new Thread(superHakceTest);        Thread thread3 = new Thread(superHakceTest);        thread1.start();thread2.start();thread3.start();        thread1.join();thread2.join();thread3.join();        System.out.println("LAST FLAG = " + SuperHakceTest.flag);    }}对象锁public class SuperHakceTest implements Runnable{    public static Integer flag = 0;    public static synchronized void instanse(){        flag ++;    }    @Override    public void run() {        for(int i = 0;i < 1000;i ++){            instanse();        }    }    public static void main(String[] args) throws Exception{        SuperHakceTest superHakceTest1 = new SuperHakceTest();        SuperHakceTest superHakceTest2 = new SuperHakceTest();        SuperHakceTest superHakceTest3 = new SuperHakceTest();        Thread thread1 = new Thread(superHakceTest1);        Thread thread2 = new Thread(superHakceTest2);        Thread thread3 = new Thread(superHakceTest3);        thread1.start();thread2.start();thread3.start();        thread1.join();thread2.join();thread3.join();        System.out.println("LAST FLAG = " + SuperHakceTest.flag);    }}//this,当前实例对象锁synchronized(this){    for(int j=0;j<1000000;j++){        i++;    }}//class对象锁synchronized(AccountingSync.class){    for(int j=0;j<1000000;j++){        i++;    }}