http://blog.csdn.net/iktz_cn/article/details/50118695 通過ThreadLoad實現線程范圍內的共享變量 線程共享變量可能出現的問題  使用ThreadLocal來避免共享變量的并發問題  實例代碼 ~~~ package cn.iktz.thread.demo; import java.util.Random; public class ThreadLocalTest2 { public static void main(String[] args) { for (int i = 0; i < 2; i++) { new Thread(new ThreadLocalTestSetData()).start(); } } } class Object1 { public void get(ThreadLocal<Integer> x) { System.out.println("A from " + Thread.currentThread().getName() + " get data :" + x.get()); } } class ThreadLocalTestSetData implements Runnable { private ThreadLocal<Integer> threadLocal = new ThreadLocal<Integer>(); @Override public void run() { int data = new Random().nextInt(); System.out.println(Thread.currentThread().getName() + " has put data :" + data); threadLocal.set(data);// threadLocl用來存儲數據，存儲的數據與當前線程有關的而非全局的 MyThreadScopeData.getThreadInstance().setName("name" + data); MyThreadScopeData.getThreadInstance().setAge(data); new Object1().get(threadLocal); } } ~~~ 對ThreadLocal進行封裝 ~~~ package cn.iktz.thread.demo; import java.util.Random; import java.util.concurrent.locks.Lock; import java.util.concurrent.locks.ReentrantLock; public class ThreadLocalTest3 { public static void main(String[] args) { for (int i = 0; i < 2; i++) { new Thread(new Runnable() { @Override public void run() { int data = new Random().nextInt(); System.out.println(Thread.currentThread().getName() + " has put data :" + data); MyThreadScopeData.getThreadInstance().setName("name" + data); MyThreadScopeData.getThreadInstance().setAge(data); new A().get(); } }).start(); } } static class A { public void get() { MyThreadScopeData myData = MyThreadScopeData.getThreadInstance(); System.out.println("A from " + Thread.currentThread().getName() + " getMyData: " + myData.getName() + "," + myData.getAge()); } } static class MyThreadScopeData { private MyThreadScopeData() { } static Lock lock = new ReentrantLock(); public static MyThreadScopeData getThreadInstance() { lock.lock(); try { MyThreadScopeData instance = map.get(); if (instance == null) { instance = new MyThreadScopeData(); /** 這里可能會出現并發問題，所以要加鎖。 這里如果a線程創建了對象，并賦值，此時instance指向0X6666， 然后b來了get為null，也會創建一個對象并賦值，此時instance指向0x7777，0x6666被覆蓋 b線程放入了0x7777的對象，此時切換到a線程，a也會放入0x7777的對象，則出現并發問題 */ map.set(instance); } return instance; } finally{ lock.unlock(); } } private static ThreadLocal<MyThreadScopeData> map = new ThreadLocal<MyThreadScopeData>(); private String name; private int age; public String getName() { return name; } public void setName(String name) { this.name = name; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } } } ~~~ 線程退出時清空該線程ThreadLocal的數據，看api可以知道，gc線程，會回收只被ThreadLocal引用的對象