ThreadLocal类的使用

变量值的共享可以使用public static变量的形式，所有的线程都是用同一个public static变量。如果想实现每一个线程都有自己的值。该变量可通过ThreadLocal实现

import javax.management.relation.RelationNotFoundException;

/**

 * @ClassName ThreadLocalExample

 * @projectName: object1

 * @author: Zhangmingda

 * @description： XXX

 * date: 2021/4/24.

 */

public class ThreadLocalExample {

    private static ThreadLocal<String> name = new ThreadLocal<>();

    public static void main(String[] args) {

        Runnable r = () -> {

            String threadname = Thread.currentThread().getName();

            /**

             * 线程运行时赋值

             */

            name.set(threadname);

            System.out.println(name.get()); //不同的子线程对应子线程名，本例A\B\C

        };

        Thread thread = new Thread(r,"A");

        Thread thread2 = new Thread(r,"B");

        Thread thread1 = new Thread(r,"C");

        thread.start();

        thread1.start();

        thread2.start();

        System.out.println(name.get()); //主线程中没有赋值默认为null

    }

}

/**

 * @ClassName ThreadLocalInitialValue

 * @projectName: object1

 * @author: Zhangmingda

 * @description： XXX

 * date: 2021/4/24.

 */

public class ThreadLocalInitialValue {

    /**

     * 定义ThreadLocal变量线程中运行自动初始化值

     */

    private static ThreadLocal<String> name = new ThreadLocal<>(){

        @Override

        protected String initialValue() {

            return Thread.currentThread().getName();

        }

    };

    public static void main(String[] args) {

        Runnable r = new Runnable() {

            @Override

            public void run() {

                System.out.println("我是" + name.get());

            }

        };

        Thread zhangsan = new Thread(r,"张三");

        Thread lisi = new Thread(r,"李四");

        zhangsan.start();

        lisi.start();

        System.out.println("main线程中，我是" + name.get());

    }

}

import java.io.Reader;

import java.sql.SQLOutput;

/**

 * @ClassName ThreadLocalSubThread

 * @projectName: object1

 * @author: Zhangmingda

 * @description： XXX

 * date: 2021/4/24.

 */

public class ThreadLocalSubThread {

    /**

     * 定义变量时，设置自动赋值方法

     */

    private static ThreadLocal<String> name = new InheritableThreadLocal<>(){

        @Override

        protected String initialValue() {

            return Thread.currentThread().getName();

        }

    };

    public static void main(String[] args) {

        Runnable r = () -> {

            System.out.println("我是子线程："+ name.get());//我是子线程：child

            Thread t = new Thread(){

                @Override

                public void run() {

                    System.out.println("我是孙线程，获取子线程变量值："+ name.get());//也是child

                }

            };

            t.start();

        };

        Thread thread = new Thread(r,"child");

        thread.start();

        name.set("主线程"); //主线程中手动赋值

        System.out.println("main线程中 name:" + name.get()); //"主线程"

    }

}