java多线程:模拟ThreadLocal

ThreadLocal存储的变量，同一线程下可见，不同线程不可见

package com.tuyrk.chapter10;

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

/**
 * 模拟ThreadLocal
 *
 */
public class ThreadLocalSimulator<T> {
    private final Map<Thread, T> storage = new HashMap<>();

    public void set(T t) {
        synchronized (this) {
            Thread key = Thread.currentThread();
            storage.put(key, t);
        }
    }

    public T get() {
        synchronized (this) {
            Thread key = Thread.currentThread();
            T value = storage.get(key);
            return value == null ? initialValue() : value;
        }
    }

    public T initialValue() {
        return null;
    }
}
//========================================================
package com.tuyrk.chapter10;

import java.util.Random;

/**
 * 模拟ThreadLocal
 *
 */
public class ThreadLocalSimulatorTest {
    private static final ThreadLocalSimulator<String> threadLocal = new ThreadLocalSimulator<String>() {
        @Override
        public String initialValue() {
            return "No Value";
        }
    };

    private static final Random RANDOM = new Random(System.currentTimeMillis());

    public static void main(String[] args) throws InterruptedException {
        Thread t1 = new Thread(() -> {
            threadLocal.set("Thread-T1");
            try {
                Thread.sleep(RANDOM.nextInt(1000));
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(Thread.currentThread().getName() + ":" + threadLocal.get());
        }, "Thread-T1");
        Thread t2 = new Thread(() -> {
            threadLocal.set("Thread-T2");
            try {
                Thread.sleep(RANDOM.nextInt(1000));
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(Thread.currentThread().getName() + ":" + threadLocal.get());
        }, "Thread-T2");
        t1.start();
        t2.start();
        t1.join();
        t2.join();

        System.out.println(Thread.currentThread().getName() + ":" + threadLocal.get());
    }
}
//OUTPUT
 /*  Thread-T2:Thread-T2
    Thread-T1:Thread-T1
    main:No Value*/