JDK ThreadLocal实例

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ThreadLocal
package org.syna.demo;

public class Demo {

public static ThreadLocal local = new ThreadLocal();

    public static int getThreadID() {
        return ((Integer) local.get()).intValue();
    }

    public static void setThreadId(int val) {
        local.set(val);
    }

    public static void main(String[] args) {
        System.out.println("main method");
        Thread thread1 = new Thread(new OtherThread(1));
        Thread thread2 = new Thread(new OtherThread(2));
        thread1.start();
        thread2.start();
    }

}

public class OtherThread implements Runnable {

    private int val;
    public OtherThread(int val) {
        this.val = val;
    }
    public void run() {
        Demo.setThreadId(val);
        for(int i=0;i<5;i++){
            System.out.println("thread "+Thread.currentThread().getId()+"-->"+val+":"+Demo.getThreadID());
            try {
                Thread.currentThread().sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }

        }
    }

}

保证变量的作用域为线程；
console:

main method
thread 7-->1:1
thread 8-->2:2
thread 7-->1:1
thread 8-->2:2
thread 7-->1:1
thread 8-->2:2
thread 7-->1:1
thread 8-->2:2
thread 7-->1:1
thread 8-->2:2

实现机理已经解释清楚了，就是在LocalThread中维护了一个Map,他的set和get会默认把currentThread作为key，所以他就能够取得一个与当前线程关联的变量，从而使得变量的线程安全；

本文来自CSDN博客，转载请标明出处：http://blog.csdn.net/turkeyzhou/archive/2008/10/13/3066219.aspx