Java中ThreadLocal的使用及原理详解

public static void main(String[] args) {
        ThreadLocal threadLocal = new ThreadLocal();
        for(int i=0;i<3;i++){
            new Thread(()->{
                double random = Math.floor(Math.random()*10);
                threadLocal.set(random);
                System.out.println("设置线程"+Thread.currentThread().getName()+",线程变量："+random);
                System.out.println("查看线程"+Thread.currentThread().getName()+",线程变量："+threadLocal.get());
            }).start();
        }
    }

 public class Thread implements Runnable {
    ThreadLocal.ThreadLocalMap threadLocals = null;
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public void set(T value) {
		//获取调用者线程
        Thread t = Thread.currentThread();
        //获取调用者线程自有的ThreadLocalMap
        ThreadLocalMap map = getMap(t);
        if (map != null)
        	//如果map！=null直接设置值
            map.set(this, value);
        else
        	//创建ThreadLocalMap，并将value存储
            createMap(t, value);
    }
    ThreadLocalMap getMap(Thread t) {
    	//获取线程的ThreadLocalMap
        return t.threadLocals;
    }
    void createMap(Thread t, T firstValue) {
    	//创建ThreadLocalMap，并设置firstValue
        t.threadLocals = new ThreadLocalMap(this, firstValue);
    }

public T get() {
		//获取调用者线程
        Thread t = Thread.currentThread();
        //获取调用者线程自有的ThreadLocalMap
        ThreadLocalMap map = getMap(t);
        if (map != null) {
        	//获取到当前ThreadLocal的值
            ThreadLocalMap.Entry e = map.getEntry(this);
            if (e != null) {
                @SuppressWarnings("unchecked")
                T result = (T)e.value;
                return result;
            }
        }
        return setInitialValue();
    }
    private T setInitialValue() {
    	//获取默认值（null），也可以重写该方法
        T value = initialValue();
        //获取调用者线程
        Thread t = Thread.currentThread();
        //获取调用者线程自有的ThreadLocalMap
        ThreadLocalMap map = getMap(t);
        if (map != null)
        	//设置为空
            map.set(this, value);
        else
        	//创建一个ThreadLocalMap,赋值为空
            createMap(t, value);
        return value;
    }

public void remove() {
	     //获取调用者线程自有的ThreadLocalMap
         ThreadLocalMap m = getMap(Thread.currentThread());
         if (m != null)
             //删除ThreadLocalMap中key为当前ThreadLocal的数据
             m.remove(this);
    }