《java多线程编程核心技术》----ThreadLocal

Posted 2022-06-18 windy13

public class Run 
    // 类ThreadLocal解决的是变量在不同线程间的隔离性，也就是 不同的线程拥有自己的值，
    // 不同线程中的值是可以放入ThreadLocal中进行保存的。
    public static ThreadLocal t1= new ThreadLocal();

    public static void main(String[] args) 
        if(t1.get()==null)
            System.out.println("从未放过值");
            t1.set("我的值");
        

        System.out.println(t1.get());
        System.out.println(t1.get());
        //从未放过值
        //我的值
        //我的值   
    

// 这里证明对应同一个threadlocal对象，不同的线程使用，线程之间是隔离的
// 线程a和线程b，同时修改threadlocal，不相互影响
public class Run 
    // 验证线程变量的隔离性
    public static ThreadLocal t1 = new ThreadLocal();

    public static void main(String[] args) 
        ThreadA a = new ThreadA();
        ThreadB b = new ThreadB();
        a.start();
        b.start();
        try 
            for (int i = 0; i < 10; i++) 
                t1.set("main" + (i + 1));
                System.out.println("main get value = " + t1.get());
                Thread.sleep(200);
            

         catch (InterruptedException e) 
            e.printStackTrace();
        

    

    static class ThreadA extends Thread 
        @Override
        public void run() 
            try 
                for (int i = 0; i < 10; i++) 
                    t1.set("ThreadA" + (i + 1));
                    System.out.println("ThreadA get value = " + t1.get());
                    Thread.sleep(200);
                

             catch (InterruptedException e) 
                e.printStackTrace();
            

        
    

    static class ThreadB extends Thread 
        @Override
        public void run() 
            try 
                for (int i = 0; i < 10; i++) 
                    t1.set("ThreadB" + (i + 1));
                    System.out.println("ThreadB get value = " + t1.get());
                    Thread.sleep(200);
                

             catch (InterruptedException e) 
                e.printStackTrace();
            

        
    


main get value = main1
ThreadA get value = ThreadA1
ThreadB get value = ThreadB1
ThreadB get value = ThreadB2
ThreadA get value = ThreadA2
main get value = main2
main get value = main3
ThreadB get value = ThreadB3
ThreadA get value = ThreadA3
ThreadA get value = ThreadA4
ThreadB get value = ThreadB4
main get value = main4
ThreadA get value = ThreadA5
ThreadB get value = ThreadB5
main get value = main5
main get value = main6
ThreadB get value = ThreadB6
ThreadA get value = ThreadA6
main get value = main7
ThreadB get value = ThreadB7
ThreadA get value = ThreadA7
ThreadA get value = ThreadA8
ThreadB get value = ThreadB8
main get value = main8
ThreadA get value = ThreadA9
ThreadB get value = ThreadB9
main get value = main9
main get value = main10
ThreadA get value = ThreadA10
ThreadB get value = ThreadB10

 

// 这里说明，每个线程保存每个线程的单独的变量，且如果线程内部可以改变的threadlocal的值
// 我们可以在其中添加我们需要的类型，这里是string类型，a线程内部，每次都改变了threadlocal的值
public class Run 

// 验证线程变量的隔离性
    public static ThreadLocal t1 = new ThreadLocal();

    public static void main(String[] args) 
        ThreadA a = new ThreadA();
        ThreadB b = new ThreadB();
        a.start();
        b.start();
    

    static class ThreadA extends Thread 
        @Override
        public void run() 
            try 
                for (int i = 0; i < 5; i++) 
                    t1.set("ThreadA" + (i + 1));
                    System.out.println("ThreadA 1 get value = " + t1.get());
                    System.out.println("ThreadA 2 get value = " + t1.get());
                    Thread.sleep(200);
                

             catch (InterruptedException e) 
                e.printStackTrace();
            

        
    

    static class ThreadB extends Thread 
        @Override
        public void run() 
            try 
                for (int i = 0; i < 5; i++) 
                    t1.set("ThreadB" + (i + 1));
                    System.out.println("ThreadB get value = " + t1.get());
                    Thread.sleep(200);
                

             catch (InterruptedException e) 
                e.printStackTrace();
            

        
    


ThreadA 1 get value = ThreadA1
ThreadA 2 get value = ThreadA1
ThreadB get value = ThreadB1
ThreadB get value = ThreadB2
ThreadA 1 get value = ThreadA2
ThreadA 2 get value = ThreadA2
ThreadB get value = ThreadB3
ThreadA 1 get value = ThreadA3
ThreadA 2 get value = ThreadA3
ThreadA 1 get value = ThreadA4
ThreadB get value = ThreadB4
ThreadA 2 get value = ThreadA4
ThreadA 1 get value = ThreadA5
ThreadB get value = ThreadB5
ThreadA 2 get value = ThreadA5