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；