ThreadLocal实现线程范围的共享变量

ThreadLocal的作用和目的：用于实现线程内的数据共享，即对于相同的程序代码，多个模块在同一个线程中运行时要共享一份数据，而在另外线程中运行时又共享另外一份数据。

一个ThreadLocal代表一个变量，故其中只能放一个数据。

例：

public class ThreadLocalTest {
private static ThreadLocal<Integer> x = new ThreadLocal<Integer>();

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()+" put data:"+data);
x.set(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);
}
}

static class B{
public void get(){
int data = x.get();
System.out.println("B from "+Thread.currentThread().getName()+" get data:"+data);
}
}
}

若要存放多个数据：

public class ThreadLocalTest02 {

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()+" put data: "+data);
MyThreadData.getThreadInstance().setName("name: "+data);
MyThreadData.getThreadInstance().setAge(data);
new A().get();
new B().get();
}
}).start();
}
}

static class A{
public void get(){
MyThreadData myData = MyThreadData.getThreadInstance();
System.out.println("A from "+Thread.currentThread().getName()+" get data: "+myData.getName()+","+myData.getAge());
}
}

static class B{
public void get(){
MyThreadData myData = MyThreadData.getThreadInstance();
System.out.println("B from "+Thread.currentThread().getName()+" get data: "+myData.getName()+","+myData.getAge());
}
}
}

class MyThreadData{
private MyThreadData() {
}

private static ThreadLocal<MyThreadData> map = new ThreadLocal<MyThreadData>();

public static MyThreadData getThreadInstance(){
MyThreadData instance = map.get();
if(instance==null){
instance = new MyThreadData();
map.set(instance);
}
return instance;
}

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;
}

}