java线程--ThreadLocal
1、package com.zhang.thread.threadlocal01;
public class Run {
public static ThreadLocal<String> t1 = new ThreadLocal<>();
public static void main(String[] args) {
if(t1.get() == null){
System.out.println("t1从来没有放过值");
t1.set("hello");
}
System.out.println(t1.get());
System.out.println(t1.get());
}
}
2、get()为空时，说明ThreadLocal中从来没有放过值；
当ThreadLocal中存在值时，可以使用get()从中取值，值依然保留
1、一个提供ThreadLocal的工具类：
public class Tools {
public static ThreadLocal<String> t1 = new ThreadLocal<>();
}
2、线程A:
public class ThreadA extends Thread {
@Override
public void run() {
try {
for(int i = 0; i < 100; i++){
Tools.t1.set("ThreadA"+(i+1));
System.out.println("ThreadA get value="+Tools.t1.get());
Thread.sleep(200);
}
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
3、线程B:
public class ThreadB extends Thread {
@Override
public void run() {
try {
for(int i = 0; i < 100; i++){
Tools.t1.set("ThreadB"+(i+1));
System.out.println("ThreadB get value="+Tools.t1.get());
Thread.sleep(200);
}
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
4、程序运行入口：
public class Run {
public static ThreadLocal<String> t1 = new ThreadLocal<>();
public static void main(String[] args) {
try {
ThreadA a = new ThreadA();
ThreadB b = new ThreadB();
a.start();
b.start();
for(int i = 0; i < 100; i++){
Tools.t1.set("Main"+(i+1));
System.out.println("Main get value="+Tools.t1.get());
Thread.sleep(200);
}
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
5、从结果可以看出：多个线程使用同一个ThreadLocal，每个线程只能取自己放入的数据