J.U.C——ThreadLocal

方法

set()

该方法会检查当前调用线程，默认以该线程的Thread.currentThread()值作为键，来保存指定的值。

    public void set(T value) {
        Thread t = Thread.currentThread();
        ThreadLocalMap map = getMap(t);
        if (map != null)
            map.set(this, value);
        else
            createMap(t, value);
    }

get()

该方法会检查当前调用线程，默认以该线程的Thread.currentThread()值作为键，获取保存指定的值。

    public T get() {
        Thread t = Thread.currentThread();
        ThreadLocalMap map = getMap(t);
        if (map != null) {
            ThreadLocalMap.Entry e = map.getEntry(this);
            if (e != null) {
                @SuppressWarnings("unchecked")
                T result = (T)e.value;
                return result;
            }
        }
        return setInitialValue();
    }

eg

package com.example.concurrent;
/**
 * @Description:
 * @Author: baxiang
 * @Date: 2021/9/28.
 */
public class ThreadLocalTest {
    static ThreadLocal<String> localVariable = new ThreadLocal<>();
    static void print(String str){
        //1.1  打印当前线程本地内存中localVariable变量的值
        System.out.println(str + ":" + localVariable.get());
        //1.2 清除当前线程本地内存中localVariable变量
        //localVariable.remove();
    }
    public static void main(String[] args) {
        //(3) 创建线程one
        Thread threadOne = new Thread(new Runnable() {
            @Override
            public void run() {
                //3.1 设置线程one中本地变量localVariable的值
                localVariable.set("threadOne local variable");
                //3.2 调用打印函数
                print("threadOne");
                //3.3打印本地变量值
                System.out.println("threadOne remove after" + ":" + localVariable.get());
            }
        });
        //(4) 创建线程two
        Thread threadTwo = new Thread(new Runnable() {
            @Override
            public void run() {
                //4.1 设置线程one中本地变量localVariable的值
                localVariable.set("threadTwo local variable");
                //4.2 调用打印函数
                print("threadTwo");
                //4.3打印本地变量值
                System.out.println("threadTwo remove after" + ":" + localVariable.get());
            }
        });
        //(5)启动线程
        threadOne.start();
        threadTwo.start();
    }
}