ThreadLocal应用实例

旧城等待， 2022-09-15 05:35 200阅读 0赞

1、ThreadLocal工具类

import java.util.Random;
    
    public class ThreadLocalUtils {
    
        public static final ThreadLocal<Object> threadLocal = new ThreadLocal<Object>() {
            @Override
            protected Object initialValue() {
                System.out.println("调用get()方法，当前线程共享变量未设置，自动调用initialValue()方法");
    //            return new Random().nextInt(100);
                return null;
            }
        };
    
    }

2、业务线程类

import lombok.SneakyThrows;
    
    import java.util.Random;
    import java.util.concurrent.TimeUnit;
    
    public class Task implements Runnable {
    
        private String name;
    
        Task(String name) {
            this.name = name;
        }
    
        @SneakyThrows
        @Override
        public void run() {
            for (int i = 1; i <= 4; i++) {
                // ThreadLocal.get方法获取本地线程变量
                if (null == ThreadLocalUtils.threadLocal.get()) {
                    Random random = new Random();
                    ThreadLocalUtils.threadLocal.set(random.nextInt(100));
    
                    int num = (Integer) ThreadLocalUtils.threadLocal.get();
                    System.out.println("线程:【" + name + "】当前值: " + num);
    
                    TimeUnit.MILLISECONDS.sleep(1000);
    
                    continue;
    
                }
    
                int num = (Integer) ThreadLocalUtils.threadLocal.get();
                num += 1;
                ThreadLocalUtils.threadLocal.set(num);
    
                System.out.println("线程:【" + name + "】当前值: " + num);
                if (i == 3) {
                    ThreadLocalUtils.threadLocal.remove();
                }
                Thread.sleep(1000);
    
            }
        }
    
    }

3、测试

public class ThreadLocalTest {
    
        public static void main(String[] args) {
    
            new Thread(new Task("task-1")).start();
            new Thread(new Task("task-2")).start();
    
        }
    
    }

4、结果

调用get()方法，当前线程共享变量未设置，自动调用initialValue()方法
    调用get()方法，当前线程共享变量未设置，自动调用initialValue()方法
    线程:【task-1】当前值: 75
    线程:【task-2】当前值: 24
    线程:【task-2】当前值: 25
    线程:【task-1】当前值: 76
    线程:【task-2】当前值: 26
    线程:【task-1】当前值: 77
    调用get()方法，当前线程共享变量未设置，自动调用initialValue()方法
    调用get()方法，当前线程共享变量未设置，自动调用initialValue()方法
    线程:【task-1】当前值: 29
    线程:【task-2】当前值: 12