ThreadLocal简析-高并发

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ThreadLocal 线程局部变量

ThreadLocal就是用空间换时间，synchronized是用时间换空间

比如在hibernate中session就是存在于Thread中，避免synchronized的使用，提高了效率

1.

package threadlocal_test;

import java.util.concurrent.TimeUnit;

public class ThreadLocal1 {
	volatile static Person p = new Person(); //volatile
	public static void main(String[] args) {
		new Thread(()->{
			try {
				TimeUnit.SECONDS.sleep(2);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
			System.out.println(p.name);
		}).start();
		
		new Thread(()->{
			try {
				TimeUnit.SECONDS.sleep(2);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
			p.name = "lisi";
		}).start();
	}
}

class Person{
	String name = "zhangsan";
}

2. 

package threadlocal_test;

import java.util.concurrent.TimeUnit;

public class ThreadLocal2 {
//	volatile static Person p = new Person(); //volatile
	static ThreadLocal<Person> tl = new ThreadLocal<>(); //ThreadLocal
	 
	public static void main(String[] args) {
		new Thread(()->{
			try {
				TimeUnit.SECONDS.sleep(2);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}

			System.out.println(tl.get()); //get()
		}).start();
		
		new Thread(()->{
			try {
				TimeUnit.SECONDS.sleep(2);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
			tl.set(new Person());
		}).start();
	}
}

使用threadLocal内存泄漏解决

tl.remove(); //不要忘了！

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