线程范围内共享变量使用ThreadLocal类详细方法

最新推荐文章于 2025-06-22 09:14:44 发布

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本文介绍了一个使用ThreadLocal实现线程间变量隔离的例子。通过自定义MyThreadScopeData类并利用ThreadLocal来存储线程特有的数据，实现了不同线程中变量值的独立存储与获取。

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class ThreadLocal<T>

其中get()方法：取得当前线程范围内共享变量的值。
set（）方法：把当前共享变量的值存到ThreadLocal（T）里面。

即get（）是得到ThreadLocal里面的共享变量值，set（）是存储ThreadLocal里面共享变量的值。

例题：线程0和线程1同时用class A和class B取得name和age两个值。

package cn.itcast.heima2;

import java.util.HashMap;
import java.util.Map;
import java.util.Random;

public class ThreadLocalTest {

	private static ThreadLocal<Integer> x = new ThreadLocal<Integer>();
	private static ThreadLocal<MyThreadScopeData> myThreadScopeData = new ThreadLocal<MyThreadScopeData>();
	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);
					x.set(data);
/*					MyThreadScopeData myData = new MyThreadScopeData();
					myData.setName("name" + data);
					myData.setAge(data);
					myThreadScopeData.set(myData);*/
					MyThreadScopeData.getThreadInstance().setName("name" + data);
					MyThreadScopeData.getThreadInstance().setAge(data);
					
					new A().get();
					new B().get();
				}
			}).start();
		}
	}
	
	static class A{
		public void get(){
			int data = x.get();
			System.out.println("A from " + Thread.currentThread().getName() 
					+ " get data :" + data);
/*			MyThreadScopeData myData = myThreadScopeData.get();;
			System.out.println("A from " + Thread.currentThread().getName() 
					+ " getMyData: " + myData.getName() + "," +
					myData.getAge());*/
			MyThreadScopeData myData = MyThreadScopeData.getThreadInstance();
			System.out.println("A from " + Thread.currentThread().getName() 
					+ " getMyData: " + myData.getName() + "," +
					myData.getAge());
		}
	}
	
	static class B{
		public void get(){
			int data = x.get();			
			System.out.println("B from " + Thread.currentThread().getName() 
					+ " get data :" + data);
			MyThreadScopeData myData = MyThreadScopeData.getThreadInstance();
			System.out.println("B from " + Thread.currentThread().getName() 
					+ " getMyData: " + myData.getName() + "," +
					myData.getAge());			
		}		
	}
}

class MyThreadScopeData{
	private MyThreadScopeData(){}         //私有化构造方法，通过getThreadInstance访问类
	public static /*synchronized*/ MyThreadScopeData getThreadInstance(){
		MyThreadScopeData instance = map.get();
		if(instance == null){
			instance = new MyThreadScopeData();
			map.set(instance);
		}
		return instance;
	}
	//private static MyThreadScopeData instance = null;//new MyThreadScopeData();
	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;
	}
}

运行结果：

Thread-0 has put data :-960708810
A from Thread-0 get data :-960708810
A from Thread-0 getMyData: name-960708810,-960708810
Thread-1 has put data :1093825706
B from Thread-0 get data :-960708810
B from Thread-0 getMyData: name-960708810,-960708810
A from Thread-1 get data :1093825706
A from Thread-1 getMyData: name1093825706,1093825706
B from Thread-1 get data :1093825706
B from Thread-1 getMyData: name1093825706,1093825706

ps：其中把Age和Name封装在MyThreadScopeData类里面，并且私有化构造方法，外面无法实例化类对象，通过单例模式在getTreadInstance方法里面定义MyThreadScopeData对面并且通过ThreadLocal<MyThreadScopeData> get得到map的值，从而实现数据的传递。

在外部main函数里面调用MyThreadScopeData的时候是通过MyThreadScopeData.getTreadInstance.set(data)设置存储MyThreadScopeData的值的。

简单说就是MyThreadScopeData定义静态方法，main函数设置存储共享变量，外部类class A和class B取得存储的共享变量，实现相同变量，不同线程使用，值不相同的效果。

这次主要运用到了java高类聚性的思想，把多个变量封装在一个类里面（避免了定义多个ThreadLocal是代码赘余），外部类调用。