threadLocal

package threadlocal;

import java.text.SimpleDateFormat;
import java.util.Date;
/*
* 两个线程打印日期
* */
public class ThreadLocalNormalUsage00 {
    public String date(int seconds){
        //参数单位是毫秒，从1970.1.1 00：00：00 GMT计时，乘以1000是转换成秒
        Date date = new Date(1000*seconds);
        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-mm-dd hh:mm:ss");
        return simpleDateFormat.format(date);
    }

    public static void main(String[] args) {
        new Thread(new Runnable() {
            @Override
            public void run() {
                String date = new ThreadLocalNormalUsage00().date(10);
                System.out.println(date);
            }
        }).start();
        new Thread(new Runnable() {
            @Override
            public void run() {
                String date = new ThreadLocalNormalUsage00().date(1007);
                System.out.println(date);
            }
        }).start();
    }
}

package threadlocal;

import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/*
* 1000个打印日期任务，使用线程池来执行
* */
public class ThreadLocalNormalUsage02 {
    public static ExecutorService threadPool = Executors.newFixedThreadPool(10);
    public String date(int seconds){
        //参数单位是毫秒
        Date date = new Date(1000*seconds);
        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-mm-dd hh:mm:ss");
        return simpleDateFormat.format(date);
    }

    public static void main(String[] args){
        for (int i = 0; i < 1000; i++) {
            int finalI = i;
            threadPool.submit(new Runnable() {
                @Override
                public void run() {
                    String date = new ThreadLocalNormalUsage02().date(finalI);
                    System.out.println(date);
                }
            });

        }
        threadPool.shutdown();
    }
}

/*
* 1000个打印日期任务，使用线程池来执行,使线程公用一个SimpleDateFormat对象，这种情况会出现线程安全问题，所以为了解决问题加锁变得安全,
* 虽然添加了锁但是在效率问题还是很低，因为添加了锁所以线程需要排队
* */
public String date(int seconds){
        //参数单位是毫秒
        Date date = new Date(1000*seconds);
        String s = null;
        synchronized (ThreadLocalNormalUsage04.class) {
            s = simpleDateFormat.format(date);
        }
        return s;
    }

package threadlocal;

import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/*
* 利用threadLocal,给每个线程分配自己的dateFormat对象，保证线程安全，高效利用内存
* */
public class ThreadLocalNormalUsage05 {
    public static void main(String[] args){
        for (int i = 0; i < 1000; i++) {
            int finalI = i;
            threadPool.submit(new Runnable() {
                @Override
                public void run() {
                    String date = new ThreadLocalNormalUsage05().date(finalI);
                    System.out.println(date);
                }
            });

        }
        threadPool.shutdown();
    }
    public static ExecutorService threadPool = Executors.newFixedThreadPool(10);
    public String date(int seconds){
        //参数单位是毫秒
        Date date = new Date(1000*seconds);
//        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-mm-dd hh:mm:ss");
        SimpleDateFormat dateFormat = ThreadSafeFormatter.dateFormatThreadLocal.get();
        return dateFormat.format(date);
    }
}
class ThreadSafeFormatter{
    public static ThreadLocal<SimpleDateFormat> dateFormatThreadLocal = new ThreadLocal<SimpleDateFormat>(){
        protected SimpleDateFormat initialValue(){
            return new SimpleDateFormat("yyyy-mm-dd hh:mm:ss");
        }
    };

}

package threadlocal;
/*
* 演示ThreadLocal用法2：避免传递参数的麻烦
* */
public class ThreadLocalNormalUsage06 {
    public static void main(String[] args) {
        new Service1().process();
    }
}
class UserContextHolder{
    public static ThreadLocal<User> holder = new ThreadLocal<>();

}
class User{
    String name;
    public User(String name) {
        this.name = name;
    }
}
class Service1{
    public void process(){
        User user = new User("tom");
        UserContextHolder.holder.set(user);
        new Service2().process();
    }
}
class Service2{
    public void process(){
        User user = UserContextHolder.holder.get();
        System.out.println("Service2拿到用户名："+user.name);
        new Service3().process();
    }
}
class Service3{
    public void process(){
        User user = UserContextHolder.holder.get();
        System.out.println("Service3拿到用户名："+user.name);
    }
}

public static ThreadLocal<SimpleDateFormat> dateFormatThreadLocal = new ThreadLocal<SimpleDateFormat>(){
        protected SimpleDateFormat initialValue(){
            return new SimpleDateFormat("yyyy-mm-dd hh:mm:ss");
        }
    };

class UserContextHolder{
    public static ThreadLocal<User> holder = new ThreadLocal<>();

}
class Service1{
    public void process(){
        User user = new User("tom");
        UserContextHolder.holder.set(user);
        new Service2().process();
    }
}