java方法同步，块同步

java方法同步，块同步 方法同步：

使用synchronized使得对象中的方法被加锁，只能被一个对象调用完之后才能被另一个对象调用。

public  class App implements Runnable
{
	
	
	 	public static void main( String[] args )
	    {
		 Counter counter =new Counter();
		 Thread thread1 =new Thread(counter,"线程一");
		 Thread thread2 = new Thread(counter,"线程二");
         thread1.start();
         thread2.start();
          
         
	    }
	
}
class Counter implements Runnable{
	int i=0;
	 synchronized void show() {
	for (; i <=3; i++) {
		System.out.println(Thread.currentThread().getName() + i);
	}
	 i=0;
}

public void run() {
	// TODO Auto-generated method stub
	show();
}

}

线程二0
线程二1
线程二2
线程二3
线程一0
线程一1
线程一2
线程一3

块同步：

当两个线程并发的访问一个对象的中的Synchronized(this)同步代码块时，一段时间只能由一个线程得到执行

package test.demo;

import java.io.Console;
import java.rmi.server.UID;
import java.util.concurrent.ThreadFactory;


public  class App implements Runnable
{
   Service service; 
   public App(Service service) {
	// TODO Auto-generated constructor stub
	super();
	this.service = service;
}	
public  static void main( String[] args )
	    {
	 Service service = new Service();
		 App app = new App(service);
		 Thread thread1 =new Thread(app,"线程一");
		 Thread thread2 = new Thread(app,"线程二");
         thread1.start();
         thread2.start();
          //两进程同时运行Service的serviceMethod()方法         
	    }

	public void run() {
		// TODO Auto-generated method stub
		service.serviceMethod();
	}
	
}
 class Service{
  void serviceMethod() {
	  try {
		synchronized (this) {//加入块同步锁，使得该语句块被某一个线程加锁，该线程执行完其他线程才能执行
			System.out.println(Thread.currentThread().getName()+"begin time ="+System.currentTimeMillis());
			Thread.sleep(1000);
			System.out.println(Thread.currentThread().getName()+"end time ="+System.currentTimeMillis());
		}
	} catch (InterruptedException e) {
		// TODO: handle exception
	 e.printStackTrace();
	}
	  
  }
}

线程一begin time =1635665200259
线程一end time =1635665201271
线程二begin time =1635665201271
线程二end time =1635665202284