JUNE ®️Jun

简介

ThreadLocal 是JDK包提供的，它提供线程本地变量，如果创建一个ThreadLocal变量，那么访问这个变量的每个线程都会有这个变量的副本，在实际多线程操作的时候，操作的都是自己本地内存中的变量，从而规避了线程安全问题。

使用

1
2
3
4
5

ThreadLocal tl = new ThreadLocal();
tl.set(k);
tl.get();
tl.remove();
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
public void set(T value) {
    Thread t = Thread.currentThread();
    ThreadLocalMap map = getMap(t);
    if (map != null)
        map.set(this, value);
    else
        createMap(t, value);
}

ThreadLocalMap getMap(Thread t) {
    return t.threadLocals;
}

void createMap(Thread t, T firstValue) {
    t.threadLocals = new ThreadLocalMap(this, firstValue);
}

Thread.java

1
2
3
4
5
6
7
8
9
/* ThreadLocal values pertaining to this thread. This map is maintained
 * by the ThreadLocal class. */
ThreadLocal.ThreadLocalMap threadLocals = null;

/*
 * InheritableThreadLocal values pertaining to this thread. This map is
 * maintained by the InheritableThreadLocal class.
 */
ThreadLocal.ThreadLocalMap inheritableThreadLocals = null;

实现原理

Thread 类中有两个变量，一个threadLocals， 一个inheritableThreadLocals。

不支持继承性

InheritableThreadLocal

内存泄漏问题