java--本地线程

Posted 2022-12-12 xanlv

同一个线程(用户)拿到同一个对象

package cn.hncu.threadLocalUtil;

import java.util.Random;

public class ThreadLocalUtil 

    private static ThreadLocal<Object> t=new ThreadLocal<Object>();
    //下面这一句是演示使用我们自己的MyThreadlocal
    //线程管理池  Map<Thread,Object>
//  private static MyThreadLocal<Object> t=new MyThreadLocal<Object>();
    public static Object getObj()
        Object obj=t.get();
        if(obj==null)
            Random r=new Random();
            obj=r.nextInt(200);
            t.set(obj);
        
        return obj;
    

package cn.hncu.threadLocalUtil;

public class Hello 

    public static void print()
        Object obj3=ThreadLocalUtil.getObj();
        Object obj4=ThreadLocalUtil.getObj();
        System.out.println("obj3:"+obj3);
        System.out.println("obj4:"+obj4);
        System.out.println(obj3==obj4);

    

package cn.hncu.threadLocalUtil;

import org.junit.Test;

public class Client 

    @Test
    public void ma() 
        Object obj1=ThreadLocalUtil.getObj();
        Object obj2=ThreadLocalUtil.getObj();
        System.out.println("obj1:"+obj1);
        System.out.println("obj2:"+obj2);
        System.out.println(obj1==obj2);

    
    //测试结果: obj1,obj2,obj3和obj4都是同一个对象 ----因为它们是同一个线程
    //       obj5和obj6是同一个对象，但 这两个对象和上面的obj1~obj4是不同的。因为这两个是另一个线程中获取出来的
    @Test
    public void threadDemo()
        Object obj1=ThreadLocalUtil.getObj();
        Object obj2=ThreadLocalUtil.getObj();
        System.out.println("obj1:"+obj1);
        System.out.println("obj2:"+obj2);
        System.out.println(obj1==obj2);

        Hello.print();
        System.out.println("======");

        new Thread()
            public void run()
                Object obj5=ThreadLocalUtil.getObj();
                Object obj6=ThreadLocalUtil.getObj();
                System.out.println("obj5:"+obj5);
                System.out.println("obj6:"+obj6);
                System.out.println(obj5==obj6);
            
        .start();

    

理解ThreadLocal原理,写一个MyThreadLocal模拟ThreadLocal类的原理功能

package cn.hncu.threadLocalUtil;

import java.util.HashMap;
import java.util.Map;

//自己模拟ThreadLocal的功能，便于大家理解该类。
//承认:虽然我们把表面功能模拟出来，但ThreadLocal真正的功能远远比这强，比如内存管理
public class MyThreadLocal<Object> 

    Map< Thread, Object> map=new HashMap<Thread, Object>();
    public Object get()
        Thread t=Thread.currentThread();
        return map.get(t);
    
    public void set(Object obj)
        Thread t=Thread.currentThread();
        map.put(t, obj);