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 ++;}@Overridepublic 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 ++;}@Overridepublic 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++;}
}