package cn.itcast.heima2; import java.util.HashMap; import java.util.Map; import java.util.Random; public class ThreadScopeShareData { private static int data = 0; private static Map<Thread, Integer> threadData = new HashMap<Thread, Integer>(); 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); threadData.put(Thread.currentThread(), data); new A().get(); new B().get(); } }).start(); } } static class A{ public void get(){ int data = threadData.get(Thread.currentThread()); System.out.println("A from " + Thread.currentThread().getName() + " get data :" + data); } } static class B{ public void get(){ int data = threadData.get(Thread.currentThread()); System.out.println("B from " + Thread.currentThread().getName() + " get data :" + data); } } }
从上面代码可以看出,这是模拟ThreadLocal的写法,其实ThreadLocal的功能就是一个以当前线程名为key的Map的存储结构。
再对上面代码进行优化,可得到这样:
package cn.itcast.heima2; import java.util.HashMap; import java.util.Map; import java.util.Random; public class ThreadScopeShareData { private static int data = 0; private static ThreadLocal<Integer> threadData = new ThreadLocal<Integer>(); 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); threadData.set(data); new A().get(); new B().get(); } }).start(); } } static class A{ public void get(){ int data = threadData.get(); System.out.println("A from " + Thread.currentThread().getName() + " get data :" + data); } } static class B{ public void get(){ int data = threadData.get(); System.out.println("B from " + Thread.currentThread().getName() + " get data :" + data); } } }
由于上面A,B两个类都属于内部静态类,所以他们可以共享变量 threadData,如果是写到外面,那么ThreadLocal<Integer>就要通过参数进行传递,如下:
package cn.itcast.heima2; import java.util.HashMap; import java.util.Map; import java.util.Random; public class ThreadScopeShareData { private static int data = 0; private static ThreadLocal<Integer> threadData = new ThreadLocal<Integer>(); 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); threadData.set(data); new A().get(threadData); new B().get(threadData); } }).start(); } } } class A{ public void get(ThreadLocal<Integer> threadData){ int data = threadData.get(); System.out.println("A from " + Thread.currentThread().getName() + " get data :" + data); } } class B{ public void get(ThreadLocal<Integer> threadData){ int data = threadData.get(); System.out.println("B from " + Thread.currentThread().getName() + " get data :" + data); } }