Java ThreadLocal application

definition

Use ThreadLocal defined variables for each thread will provide a copy of a separate thread. Simply, a thread a singleton.

Simple examples

import java.util.Random;
public class ThreadLocalTestMain {
    public static void main(String[] args) throws Throwable {
        Thread t= new Thread(()->{
            System.out.println("线程ID"+Thread.currentThread().getId()+ ";ID值:"+ThreadLocalTest.getId());
        });
        Thread t2= new Thread(()->{
            System.out.println("线程ID"+Thread.currentThread().getId()+ ";ID值:"+ThreadLocalTest.getId());
            System.out.println("线程ID"+Thread.currentThread().getId()+ ";ID值:"+ThreadLocalTest.getId());
            System.out.println("线程ID"+Thread.currentThread().getId()+ ";ID值:"+ThreadLocalTest.getId());
            System.out.println("线程ID"+Thread.currentThread().getId()+ ";ID值:"+ThreadLocalTest.getId());
            System.out.println("线程ID"+Thread.currentThread().getId()+ ";ID值:"+ThreadLocalTest.getId());
        });
        Thread t3= new Thread(()->{
            System.out.println("线程ID"+Thread.currentThread().getId()+ ";ID值:"+ThreadLocalTest.getId());
        });
        t.start();
        t2.start();
        t3.start();
    }
    public static class ThreadLocalTest {
        private static ThreadLocal<Integer> ids = ThreadLocal.withInitial(() -> {
            System.out.println("线程ID"+Thread.currentThread().getId()+ ";ids值初始化");
            return  new Random().nextInt(10000);
        });
        public static Integer getId() {
            return ids.get();
        }
    }

}

Output

Thread ID12; ids initializes the value of
the thread ID14; ids initializes the value of
the thread ID13; ids initializes the value of
the thread ID12; ID Found: 2137
thread ID14; ID Found: 7831
thread ID13; ID Found: 1443
thread ID13; ID Found: 1443
thread ID13; ID Found: 1443
thread ID13; ID Found: 1443
thread ID13; ID Found: 1443

Result analysis

1: Each thread has one and only one initialization.
2: a thread calls only gid, and will not touch initialization.
3: 1,2 Comprehensive above conclusion drawn: a one-way line embodiment.