如果我不同步方法，则后台发生了什么，导致应用程序在控制台什么都不打印的情况下运行？

Question

我有一个具有两个线程的主类。这两个线程运行在其他类中定义的两个方法。

WaitNotifyMain.java

package com.practice.multithreading;

public class WaitNotifyMain {

    public static void main(String[] args) {
        WaitNotify waitNotify = new WaitNotify();
        Thread t1 = new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    waitNotify.produce();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        });

        // lambda expressions Java 8
        Thread t2 = new Thread(() -> {
            try {
                waitNotify.consume();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        });

        t1.start();
        t2.start();

        try {
            t1.join();
            t2.join();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }


    }

}

WaitNotify.java

package com.practice.multithreading;

import java.util.LinkedList;
import java.util.List;

public class WaitNotify {


    /*created an object of linkedlist without Polymorphism  as we require 
    removeFIrst() method which is specific to the linkedList class*/
    private LinkedList<Integer> list = new LinkedList<Integer>();

    private final int LIMIT=10;

    public void produce() throws InterruptedException{
        int value = 0;
        while(true) {

            while(list.size()!=LIMIT) {
            list.add(value++);
            System.out.println("Added an element");

            }

        }

    }

    public void consume() throws InterruptedException{

        while(true) {
            while(!list.isEmpty()) {
                System.out.print("List size :"+list.size());
                int value = list.removeFirst();
                System.out.println("; value is: " +value);

            }

        }
    }
}

输出

Added an element
Added an element
Added an element
Added an element
Added an element
Added an element
Added an element
Added an element
Added an element
Added an element
List size :1Added an element
; value is: 0
List size :10Added an element
; value is: 1
List size :10Added an element
; value is: 2
List size :10Added an element
; value is: 3
List size :10Added an element
; value is: 4
List size :10Added an element
; value is: 5
List size :10Added an element
; value is: 6
List size :10Added an element
; value is: 7
List size :10Added an element
; value is: 8
List size :10Added an element
; value is: 9
List size :10Added an element
; value is: 10
List size :10Added an element
; value is: 11
List size :10Added an element
; value is: 12
List size :10; value is: 13
List size :10; value is: 14
List size :9; value is: 15
List size :8; value is: 16
List size :7; value is: 17
List size :6; value is: 18
List size :5; value is: 19
List size :4Added an element
Added an element
Added an element
Added an element
Added an element
Added an element
Added an element
Added an element
; value is: 20
List size :10; value is: 21
List size :10; value is: 22
List size :9; value is: 23
List size :8; value is: 24
List size :7; value is: 25
List size :6; value is: 26
List size :5; value is: 27
List size :4; value is: 28
List size :3; value is: 29
List size :2; value is: 30
List size :1; value is: 31
Added an element
Added an element
Added an element
Added an element
Added an element
Added an element
Added an element
Added an element
Added an element
Added an element
Added an element
List size :1Added an element
; value is: 32
List size :10Added an element
; value is: 33
List size :10Added an element
; value is: 34
List size :10Added an element
; value is: 35
List size :10Added an element
; value is: 36
List size :10; value is: 37
List size :10Added an element
Added an element
; value is: 38
List size :10Added an element
; value is: 39
List size :10Added an element
; value is: 40
List size :10Added an element
; value is: 41
List size :10Added an element
; value is: 42
List size :10Added an element
; value is: 43
List size :10Added an element
; value is: 44
List size :10Added an element
; value is: 45
List size :10Added an element
; value is: 46
List size :10Added an element
; value is: 47
List size :10Added an element
; value is: 48
List size :10Added an element
; value is: 49
List size :10Added an element
; value is: 50
List size :10Added an element
; value is: 51
List size :10Added an element
; value is: 52
List size :10Added an element
; value is: 53
List size :10Added an element
; value is: 54
List size :10Added an element
; value is: 55
List size :10Added an element
; value is: 56
List size :10Added an element
; value is: 57
List size :10Added an element
; value is: 58
List size :10Added an element
; value is: 59
List size :10Added an element
; value is: 60
List size :10Added an element
; value is: 61
List size :10Added an element
; value is: 62
List size :10Added an element
; value is: 63
List size :10Added an element
; value is: 64
List size :10Added an element
; value is: 65
List size :10Added an element
; value is: 66
List size :10Added an element
; value is: 67
List size :10Added an element
; value is: 68
List size :10Added an element
; value is: 69
List size :10Added an element
; value is: 70
List size :10Added an element
; value is: 71
List size :10Added an element
; value is: 72
List size :10Added an element
; value is: 73
List size :10Added an element
; value is: 74
List size :10Added an element
; value is: 75
List size :10Added an element
; value is: 76
List size :10Added an element
; value is: 77
List size :10Added an element
; value is: 78
List size :10Added an element
; value is: 79
List size :10Added an element
; value is: 80
List size :10Added an element
; value is: 81
List size :10Added an element
; value is: 82
List size :10Added an element
; value is: 83
List size :10Added an element
; value is: 84
List size :10Added an element
; value is: 85
List size :10Added an element
; value is: 86
List size :10Added an element
; value is: 87
List size :10Added an element
; value is: 88
List size :10Added an element
; value is: 89
List size :10Added an element
; value is: 90
List size :10Added an element
; value is: 91
List size :10Added an element
; value is: 92
List size :10Added an element
; value is: 93
List size :10Added an element
; value is: 94
List size :10Added an element
; value is: 95
List size :10; value is: 96
List size :10; value is: 97
List size :9; value is: 98
List size :8; value is: 99
List size :7Added an element
Added an element
Added an element
Added an element
Added an element
; value is: 100
List size :10; value is: 101
List size :9; value is: 102
List size :8; value is: 103
List size :7; value is: 104
List size :6; value is: 105
List size :5; value is: 106
List size :4; value is: 107
List size :3; value is: 108
List size :2; value is: 109
List size :1; value is: 110

>>>>>>>after this nothing in console<<<<<<<<<<<<<

我了解，由于未同步，因此无法按预期运行，并且每次运行时都会得到diff输出。

但是我的问题是，为什么控制台显示我的应用程序一直运行，而我在控制台中看不到任何输出。

有人可以解释这种行为吗？

Answer 1

在两个while(true)循环中添加输出，您将看到其中一个线程被卡住，可能另一个线程未获得量子时间。