package day1;

import java.util.HashMap;
import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.CyclicBarrier;
import java.util.concurrent.TimeUnit;

public class ThreadLocalTest {
    static CyclicBarrier c = new CyclicBarrier(2);
    private ThreadLocal<HashMap<String,String>> mapLocal = new
 
 ThreadLocal<HashMap<String,String>>(){
        @Override
        protected HashMap<String,String> initialValue() {
            return new HashMap<String,String>();
        }
    };
    private HashMap<String,String> hashMap= new HashMap<String,String>();
    public
 
 void put(String key,String value) {
        HashMap<String,String> hashMap = mapLocal.get();
        if(hashMap == null) {
            System.out.println("=======");
            hashMap = new HashMap<String,String>();
        }
        hashMap.put(key, value);
        mapLocal.set(hashMap);
    }
    public
 
 String get(String key) {
        return mapLocal.get().get(key);
    }

    public HashMap<String, String> getHashMap() {
        return hashMap;
    }
    public void setHashMap(HashMap<String, String> hashMap) {
        this.hashMap = hashMap;
    }
    public static void main(String[] args) throws Exception {
        ThreadLocalTest profiler=new ThreadLocalTest();
        for(int i =0;i<6;i++) {
            new Thread("thread"+i) {
                public void run() {
                    try {
                        c.await();
                    } catch (InterruptedException e1) {
                        // TODO Auto-generated catch block
                        e1.printStackTrace();
                    } catch (BrokenBarrierException e1) {
                        // TODO Auto-generated catch block
                        e1.printStackTrace();
                    }
                    profiler.put("name", Thread.currentThread().getName());
                    try {
                        TimeUnit.SECONDS.sleep(2);
                        System.out.println(Thread.currentThread().getName()+":"
                                +profiler.get("name"));
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }.start();
        }
        for(int i =6;i<12;i++) {
            new Thread("thread"+i) {
                public void run() {
                    try {
                        c.await();
                    } catch (InterruptedException e1) {
                        // TODO Auto-generated catch block
                        e1.printStackTrace();
                    } catch (BrokenBarrierException e1) {
                        // TODO Auto-generated catch block
                        e1.printStackTrace();
                    }
                    try {
                        TimeUnit.SECONDS.sleep(2);
                    } catch (InterruptedException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                    profiler.getHashMap().put("name", Thread.currentThread().getName());
                        System.out.println(Thread.currentThread().getName()+":"
                                +profiler.getHashMap().get("name"));

                }
            }.start();
        }
    }
}

console輸出：

thread8:thread9
thread9:thread9
thread6:thread11
thread10:thread11
thread11:thread11
thread0:thread0
thread1:thread1
thread2:thread2
thread4:thread4
thread3:thread3
thread7:thread7
thread5:thread5

執行緒0-5中的name的值跟執行緒名是一一對應的，6-11則每次執行的時候都會不一樣，所以ThreadLocal可用於保證執行緒安全，每個執行緒都保有一個ThreadLocal