ThreadLocal类及应用技巧
（1）非线程内的数据共享：
public class ThreadScopeShareData {
private static int shareData;
public static void main(String[] args){
for(int i=0;i<2;i++){
new Thread(new Runnable() {
@Override
public void run() {
shareData= new Random().nextInt();
System.out.println(Thread.currentThread().getName()+"has put "+shareData);
new A().get();
new B().get();
}
}).start();
}
}
static class A{
public void get(){
System.out.println("A from "+Thread.currentThread().getName()+" get data "+shareData);
}
}
static class B{
public void get(){
System.out.println("B from "+Thread.currentThread().getName()+" get data "+shareData);
}
}
}
（2）自己实现线程内的共享：
/**
* 实现线程内的共享数据
*/
public class ThreadScopeShareData {
private static Integer data=0;
private static ReentrantLock reentrantLock = new ReentrantLock();
private static Map<Thread,Integer> map=new HashMap<>();
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();
map.put(Thread.currentThread(),data);
System.out.println(Thread.currentThread().getName()+" has put "+data);
new A().get();
new B().get();
}
}).start();
}
}
static class A{
public void get(){
Integer data = map.get(Thread.currentThread());
System.out.println("A from "+Thread.currentThread().getName()+" get data "+data);
}
}
static class B{
public void get(){
Integer data = map.get(Thread.currentThread());
System.out.println("B from "+Thread.currentThread().getName()+" get data "+data);
}
}
//注意代码是有问题的，会出现重排序的问题：
Thread-0 has put 845819596
Thread-1 has put 1724703386
A from Thread-0 get data null
A from Thread-1 get data 1724703386
B from Thread-0 get data null
B from Thread-1 get data 1724703386
//更改一下：更改顺序，就不会有问题了。
int data= new Random().nextInt();
System.out.println(Thread.currentThread().getName()+" has put "+data);
map.put(Thread.currentThread(),data);
new A().get();
new B().get();
}
}).start();
实际应用，比如线程池。
（3）工具实现线程内数据的共享：
public class ThreadLocalTest {
private static ThreadLocal<Integer> threadLocal=new ThreadLocal();
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);
threadLocal.set(data);
new A().get();
new B().get();
}
}).start();
}
}
static class A{
public void get(){
Integer data = threadLocal.get();
System.out.println("A from "+Thread.currentThread().getName()+" get data "+data);
}
}
static class B{
public void get(){
Integer data = threadLocal.get();
System.out.println("B from "+Thread.currentThread().getName()+" get data "+data);
}
}
}
（4）多个值的线程内数据的共享
/**
*实体线程内数据共享
*/
public class ThreadLocalInstance {
private static ThreadLocal<MyThreadScopeData> threadLocal=new ThreadLocal<>();
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);
MyThreadScopeData myThreadScopeData = new MyThreadScopeData();
myThreadScopeData.setName(String.valueOf(data));
myThreadScopeData.setAge(data);
threadLocal.set(myThreadScopeData);
new A().get();
new B().get();
}
}).start();
}
}
static class A{
public void get(){
MyThreadScopeData myThreadScopeData = threadLocal.get();
System.out.println("A from "+Thread.currentThread().getName()+" get name "+ myThreadScopeData.getName());
System.out.println("A from "+Thread.currentThread().getName()+" get age "+ myThreadScopeData.getAge());
}
}
static class B{
public void get(){
MyThreadScopeData myThreadScopeData = threadLocal.get();
System.out.println("B from "+Thread.currentThread().getName()+" get name "+ myThreadScopeData.getName());
System.out.println("B from "+Thread.currentThread().getName()+" get age "+ myThreadScopeData.getAge());
}
}
static class 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;
}
}
}
（5）多个值的线程内数据共享的优化
package com.renrenche.thread;
import java.util.Random;
/**
*实体线程内数据共享
*/
public class ThreadLocalInstance {
private static ThreadLocal<MyThreadScopeData> threadLocal=new ThreadLocal<>();
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);
MyThreadScopeData myThreadScopeData = MyThreadScopeData.getMyThreadScopeInstatnce();
myThreadScopeData.setName(String.valueOf(data));
myThreadScopeData.setAge(data);
threadLocal.set(myThreadScopeData);
new A().get();
new B().get();
}
}).start();
}
}
static class A{
public void get(){
MyThreadScopeData myThreadScopeData = MyThreadScopeData.getMyThreadScopeInstatnce();
System.out.println("A from "+Thread.currentThread().getName()+" get name "+ myThreadScopeData.getName());
System.out.println("A from "+Thread.currentThread().getName()+" get age "+ myThreadScopeData.getAge());
}
}
static class B{
public void get(){
MyThreadScopeData myThreadScopeData = MyThreadScopeData.getMyThreadScopeInstatnce();
System.out.println("B from "+Thread.currentThread().getName()+" get name "+ myThreadScopeData.getName());
System.out.println("B from "+Thread.currentThread().getName()+" get age "+ myThreadScopeData.getAge());
}
}
static class MyThreadScopeData{
private static ThreadLocal<MyThreadScopeData> threadLocal=new ThreadLocal<>();
private MyThreadScopeData(){
}
public static synchronized MyThreadScopeData getMyThreadScopeInstatnce(){
MyThreadScopeData myThreadScopeData = threadLocal.get();
if(myThreadScopeData==null){
myThreadScopeData=new MyThreadScopeData();
threadLocal.set(myThreadScopeData);
}
return 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;
}
}
}
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github: https://github.com/wangrui0/