ThreadLocal的作用

左手的ㄟ右手 2022-06-13 13:57 47阅读 0赞

例子一：

public class Test6 extends Thread{
    public static void main(String[] args) {
    	new Test6().start();
    	new Test6().start();
    }
    public void run(){
    	test();
    }
    static ThreadLocal<Integer> local=new ThreadLocal<Integer>();
    //ThreadLocal是用资源空间换取时间的做法
    //ThreadLocal底层代码使用一个静态的内部类ThreadLocalMap存储副本变量，好让另一个线程使用
    static int num;
    public void test(){
    	while(true){
    		try {
    			Thread.sleep(1000);
    		} catch (InterruptedException e) {
    			e.printStackTrace();
    		}
    		System.out.println(Thread.currentThread().getName()+"::"+local.get()+"::"+num++);
    		if(local.get()==null){
    			local.set(0);
    		}else{
    			int temp=local.get();
    			local.set(++temp);
    		}
    	}
    }
    }
    /*
      输出结果如下：
      	Thread-0::null::0
    	Thread-1::null::1
    	Thread-0::0::2
    	Thread-1::0::3
    	Thread-0::1::4
    	Thread-1::1::5
    	Thread-0::2::6
    	Thread-1::2::7
    	Thread-0::3::8
    	Thread-1::3::9
    */

例子二：

public class Test8 {
    static Map<Thread,Integer> map=new HashMap<Thread,Integer>();
    //static int data;
    public static void main(String[] args) {
    	for(int i=0;i<2;i++){
    		new Thread(){
    			public void run(){
    				int num=new Random().nextInt();
    				System.out.println("has put : "+num);
    //				data=num;
    				map.put(Thread.currentThread(), num);
    				new A().getData();
    				new B().getData();
    			}
    		}.start();
    	}
    }
    static class A{
    	public void getData(){
    		System.out.println(Thread.currentThread().getName()+": A data:"+/*data*/map.get(Thread.currentThread()));
    	}
    }
    static class B{
    	public void getData(){
    		System.out.println(Thread.currentThread().getName()+": B data:"+/*data*/map.get(Thread.currentThread()));
    	}
    }
    }

例子三：

public class Test9 {
    public static void main(String[] args) {
    	for(int i=0;i<2;i++){
    		new Thread(new Runnable(){
    			public void run(){
    				int num=new Random().nextInt();
    				MyThreadScopeData ins=MyThreadScopeData.getThreadInstance();
    				System.out.println(Thread.currentThread().getName()+":num:"+num);
    				ins.setData(num);
    				ins.setName("name:"+num);
    				ins.getData();
    				ins.getName();
    			}
    		}).start();
    	}
    }
    }
    class MyThreadScopeData{
    	private static ThreadLocal<MyThreadScopeData> local=new ThreadLocal<MyThreadScopeData>();
    	private MyThreadScopeData(){}//单例模式
    	public static MyThreadScopeData getThreadInstance(){
    		MyThreadScopeData mythread=local.get();
    		if(mythread==null){
    			local.set(new MyThreadScopeData());
    		}
    		return local.get();
    	}
    	private String name;
    	private Integer data;
    	public void getName() {
    		System.out.println(Thread.currentThread().getName()+":"+name);
    	}
    	public void setName(String name) {
    		this.name = name;
    	}
    	public void getData() {
    		System.out.println(Thread.currentThread().getName()+":"+data);
    	}
    	public void setData(Integer data) {
    		this.data = data;
    	}
    }