手写自己的ThreadLocal（线程局部变量）

ThreadLocal对象通常用于防止对可变的单实例变量或全局变量进行共享。

精简版：

public class MyThreadLocal<T> {
    private Map<Thread, T> map = Collections.synchronizedMap(new HashMap<Thread, T>());

    public void set(T newValue) {
        map.put(Thread.currentThread(), newValue);
    }

    public T get() {
        return map.get(Thread.currentThread());
    }

    public void remove() {
        map.remove(Thread.currentThread());
    }
}

package com.lxc.tet;

import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

public class MyThreadLocal<T> {
    private Map<Thread,T> map = new ConcurrentHashMap<Thread, T>();

    protected T initialValue(){
        return null;
    }

    public void set(T value){
        map.put(Thread.currentThread(), value);
    }

    public T get(){
        T result = null;
        result = map.get(Thread.currentThread());
        if(result==null && !map.containsKey(Thread.currentThread())){
            result=initialValue();
            set(result);
        }
        return result;
    }

    public void remove(){
        map.remove(Thread.currentThread());
    }
}