0

我正在尝试最近学习的一些多线程概念，但无法运行它。

它给出了 IllegalMonitorStateException 但没有弄清楚为什么会发生错误。

所以关于code-2线程-引用名称-填充器和写入器都共享一个arraylist-filler正在用整数填充arraylist（但将填充到30）并且在填充器和写入器线程添加每个数字之后读取arraylist获取项目将其写入文件，将其从 arraylist 中删除。为了更好地理解注释被添加到代码中。

package com.utsav.pratice;

import java.io.*;
import java.util.ArrayList;

public class Main {

    public static void main(String[] args) throws FileNotFoundException {
        //shared arraylist-synchronized
        ArrayList<Integer> integerArrayList = new ArrayList<>();
        //writter will write to this file numbers added to arraylist by filler and than will remove it from arraylist
        FileOutputStream file = new FileOutputStream("Numbers.txt");
        //filler will mark it true after completing all numbers
        final boolean[] numbersCompleted = {false};

        Thread filler=new Thread(new Runnable(){
            @Override
            public void run(){
                //1-30 numbers one by one will be written to Arraylist
                for (int i = 1; i < 31; i++) {
                    synchronized (integerArrayList) {
                        //if arraylist is not empty that means writter not performed on arraylist hence invoking wait to release lock so writter could perform
                        while(!integerArrayList.isEmpty()){
                            try {
                                wait();
                            } catch (InterruptedException e) {
                                e.printStackTrace();
                            }
                        }
                        //so arraylist is empty now lets fill it,notify that releasing lock and than put thread to sleep
                        integerArrayList.add(i);
                        System.out.println("Number added");
                        if(i==30){
                            numbersCompleted[0] =true;}
                        notifyAll();
                    }
                    try {
                        Thread.sleep(2000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
                System.out.println("Numbers adding completed");
            }
        });

        Thread writter=new Thread(new Runnable(){
            @Override
            public void run(){
                //if numbers are completed than nothing to write come out of loop
                while(!numbersCompleted[0]) {
                    synchronized (integerArrayList) {
                        //if arraylist is empty than its time for filler to work hence putting thread to wait so lock could be released for filler
                        while (integerArrayList.isEmpty()){
                            try {
                                wait();
                            } catch (InterruptedException e) {
                                e.printStackTrace();
                            }
                        }
                        //so arraylist is not empty now lets write it & than remove it from arraylist,notify that releasing lock and than put thread to sleep
                        try (DataOutputStream fileWritter = new DataOutputStream(new BufferedOutputStream(file));) {
                            fileWritter.writeInt(integerArrayList.get(0));
                            System.out.println("Random number written");
                        } catch (IOException e) {
                            e.printStackTrace();
                        }
                        integerArrayList.remove(0);
                        notifyAll();
                    }
                    try {
                        Thread.sleep(2000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
                System.out.println("File written completely");
            }
        });

        //starting both threads-2cases filler takes the key-ok(will fill & wait) or filler takes the key(will wait since will be empty)
        writter.start();
        filler.start();
4

1 回答 1

1

这里：

synchronized (integerArrayList)

您正在同步您的列表。

但是您正在等待/通知您的匿名线程对象！正如javadoc中的第一条信息所说：

抛出以指示线程已尝试在对象的监视器上等待，或通知其他线程在对象的监视器上等待而不拥有指定的监视器。

因此，当您将其更改为

integerArrayList.wait()

例如（等待/通知/...的所有用法）！

并提示：不要做类似的事情

final ArrayList<Integer> integerArrayList = new ArrayList<>();

去吧

List<Integer> numbers = new ArrayList<>();

只是不要使用具体的 impl 类类型作为变量的类型；也不是它名字的一部分！

于 2017-03-03T08:38:40.693 回答