玩转Java并发工具精通JUC成为并发多面手【15章完整版】笔记汇总 ThreadLocal 代码详解

2022-03-16 03:47:23

对Java并发常见的工具类进行从使用到原理的详解，
包括CAS+AQS+ThreadLocal+ConcurrentHashMap+线程池+各种锁+并发综合实战项目

下载：链接：https://pan.baidu.com/s/1u6xXLnNUd7jBqw7dxoymeQ
提取码：9voy

package threadlocal;

import java.text.SimpleDateFormat;
import java.util.Date;

/**
 * 描述：     两个线程打印日期
 */
public class ThreadLocalNormalUsage00 {

    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(104707);
                System.out.println(date);
            }
        }).start();
    }

    public String date(int seconds) {
        //参数的单位是毫秒，从1970.1.1 00:00:00 GMT计时
        Date date = new Date(1000 * seconds);
        SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        return dateFormat.format(date);
    }
}

下载：链接：https://pan.baidu.com/s/1u6xXLnNUd7jBqw7dxoymeQ
提取码：9voy

package threadlocal;

import java.text.SimpleDateFormat;
import java.util.Date;

/**
 * 描述：     10个线程打印日期
 */
public class ThreadLocalNormalUsage01 {

    public static void main(String[] args) throws InterruptedException {
        for (int i = 0; i < 30; i++) {
            int finalI = i;
            new Thread(new Runnable() {
                @Override
                public void run() {
                    String date = new ThreadLocalNormalUsage01().date(finalI);
                    System.out.println(date);
                }
            }).start();
            Thread.sleep(100);
        }

    }

    public String date(int seconds) {
        //参数的单位是毫秒，从1970.1.1 00:00:00 GMT计时
        Date date = new Date(1000 * seconds);
        SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        return dateFormat.format(date);
    }
}

package threadlocal;

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

/**
 * 描述：     1000个打印日期的任务，用线程池来执行
 */
public class ThreadLocalNormalUsage02 {

    public static ExecutorService threadPool = Executors.newFixedThreadPool(10);

    public static void main(String[] args) throws InterruptedException {
        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();
    }

    public String date(int seconds) {
        //参数的单位是毫秒，从1970.1.1 00:00:00 GMT计时
        Date date = new Date(1000 * seconds);
        SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        return dateFormat.format(date);
    }
}

package threadlocal;

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

/**
 * 描述：     加锁来解决线程安全问题
 */
public class ThreadLocalNormalUsage04 {

    public static ExecutorService threadPool = Executors.newFixedThreadPool(10);
    static SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

    public static void main(String[] args) throws InterruptedException {
        for (int i = 0; i < 1000; i++) {
            int finalI = i;
            threadPool.submit(new Runnable() {
                @Override
                public void run() {
                    String date = new ThreadLocalNormalUsage04().date(finalI);
                    System.out.println(date);
                }
            });
        }
        threadPool.shutdown();
    }

    public String date(int seconds) {
        //参数的单位是毫秒，从1970.1.1 00:00:00 GMT计时
        Date date = new Date(1000 * seconds);
        String s = null;
        synchronized (ThreadLocalNormalUsage04.class) {
            s = dateFormat.format(date);
        }
        return s;
    }
}

package threadlocal;

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

/**
 * 描述：     利用ThreadLocal，给每个线程分配自己的dateFormat对象，保证了线程安全，高效利用内存
 */
public class ThreadLocalNormalUsage05 {

    public static ExecutorService threadPool = Executors.newFixedThreadPool(10);

    public static void main(String[] args) throws InterruptedException {
        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 String date(int seconds) {
        //参数的单位是毫秒，从1970.1.1 00:00:00 GMT计时
        Date date = new Date(1000 * seconds);
//        SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        SimpleDateFormat dateFormat = ThreadSafeFormatter.dateFormatThreadLocal2.get();
        return dateFormat.format(date);
    }
}

class ThreadSafeFormatter {

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

    public static ThreadLocal<SimpleDateFormat> dateFormatThreadLocal2 = ThreadLocal
            .withInitial(() -> new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"));
}

package threadlocal;

/**
 * 描述：     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 Service1 {

    public void process(String name) {
        User user = new User("超哥");
        UserContextHolder.holder.set(user);
        new Service2().process();
    }
}

class Service2 {

    public void process() {
        User user = UserContextHolder.holder.get();
        ThreadSafeFormatter.dateFormatThreadLocal.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);
        UserContextHolder.holder.remove();
    }
}

class UserContextHolder {

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


}

class User {

    String name;

    public User(String name) {
        this.name = name;
    }
}

下载：链接：https://pan.baidu.com/s/1u6xXLnNUd7jBqw7dxoymeQ
提取码：9voy

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