Java:为什么我更新哈希表中一个特定的键的数组值会改变所有其他的键值?

我需要你的帮助,因为我不知道为什么我更新的哈希图中的一个值(对于一个特定的键)几乎改变了所有其他键的值… 下面是您可以尝试的相应代码:

import edu.duke.*;
import java.util.*;
import java.io.*;

public class WordsInFiles {
    private HashMap<String, ArrayList> map;

    public WordsInFiles(){
        map = new HashMap<String, ArrayList>();
    }

    private void addWordsFromFile(File f) {
        FileResource fr = new FileResource(f);
        String fileName = f.getName();
        ArrayList<String> newWord = new ArrayList<String>();
        for (String s : fr.words()){
            if (!map.containsKey(s)) {
                newWord.clear();
                newWord.add(fileName);
                map.put(s, newWord);
                System.out.println("New:" + s + "\t" + newWord);
            } else {
                ArrayList<String> currArr = map.get(s);
                if (!currArr.contains(fileName)){
                    currArr.add(fileName);
                    newWord = currArr;
                    System.out.println("Update:" +s + "\t" + newWord);
                    map.put(s, newWord);
                }
            }
            System.out.println(map + "\n");
        }
    }

    public void tester() {
        System.out.println("\n ****** New Tester Instance ****** ");
        buildWordFileMap();
    }
}

通过在分别包含字符串的4个文件上运行检测仪:brief1.txt、brief2.txt、brief3.txt和brief4.txt:

1. 猫又有趣又可爱
2. 狗是愚蠢的
3. 爱动物猫狗
4. 爱鸟爱猫

我得到:

 ****** New Tester Instance ****** 
New:cats    [brief1.txt]
{cats=[brief1.txt]}

New:are [brief1.txt]
{cats=[brief1.txt], are=[brief1.txt]}

New:funny   [brief1.txt]
{cats=[brief1.txt], are=[brief1.txt], funny=[brief1.txt]}

New:and [brief1.txt]
{cats=[brief1.txt], are=[brief1.txt], and=[brief1.txt], funny=[brief1.txt]}

New:cute    [brief1.txt]
{cats=[brief1.txt], are=[brief1.txt], and=[brief1.txt], cute=[brief1.txt], funny=[brief1.txt]}

New:dogs    [brief2.txt]
{cats=[brief1.txt], are=[brief1.txt], and=[brief1.txt], dogs=[brief2.txt], cute=[brief1.txt], funny=[brief1.txt]}

Update:are  [brief1.txt, brief2.txt]
{cats=[brief1.txt, brief2.txt], are=[brief1.txt, brief2.txt], and=[brief1.txt, brief2.txt], dogs=[brief2.txt], cute=[brief1.txt, brief2.txt], funny=[brief1.txt, brief2.txt]}

New:silly   [brief2.txt]
{cats=[brief2.txt], are=[brief2.txt], and=[brief2.txt], silly=[brief2.txt], dogs=[brief2.txt], cute=[brief2.txt], funny=[brief2.txt]}

New:love    [brief3.txt]
{love=[brief3.txt], cats=[brief2.txt], are=[brief2.txt], and=[brief2.txt], silly=[brief2.txt], dogs=[brief2.txt], cute=[brief2.txt], funny=[brief2.txt]}

New:animals [brief3.txt]
{love=[brief3.txt], cats=[brief2.txt], are=[brief2.txt], and=[brief2.txt], silly=[brief2.txt], dogs=[brief2.txt], animals=[brief3.txt], cute=[brief2.txt], funny=[brief2.txt]}

Update:cats [brief2.txt, brief3.txt]
{love=[brief3.txt], cats=[brief2.txt, brief3.txt], are=[brief2.txt, brief3.txt], and=[brief2.txt, brief3.txt], silly=[brief2.txt, brief3.txt], dogs=[brief2.txt], animals=[brief3.txt], cute=[brief2.txt, brief3.txt], funny=[brief2.txt, brief3.txt]}

{love=[brief3.txt], cats=[brief2.txt, brief3.txt], are=[brief2.txt, brief3.txt], and=[brief2.txt, brief3.txt], silly=[brief2.txt, brief3.txt], dogs=[brief2.txt], animals=[brief3.txt], cute=[brief2.txt, brief3.txt], funny=[brief2.txt, brief3.txt]}

Update:dogs [brief2.txt, brief3.txt]
{love=[brief3.txt], cats=[brief2.txt, brief3.txt], are=[brief2.txt, brief3.txt], and=[brief2.txt, brief3.txt], silly=[brief2.txt, brief3.txt], dogs=[brief2.txt, brief3.txt], animals=[brief3.txt], cute=[brief2.txt, brief3.txt], funny=[brief2.txt, brief3.txt]}

Update:love [brief3.txt, brief4.txt]
{love=[brief3.txt, brief4.txt], cats=[brief2.txt, brief3.txt], are=[brief2.txt, brief3.txt], and=[brief2.txt, brief3.txt], silly=[brief2.txt, brief3.txt], dogs=[brief2.txt, brief3.txt], animals=[brief3.txt, brief4.txt], cute=[brief2.txt, brief3.txt], funny=[brief2.txt, brief3.txt]}

New:birds   [brief4.txt]
{love=[brief4.txt], cats=[brief2.txt, brief3.txt], are=[brief2.txt, brief3.txt], and=[brief2.txt, brief3.txt], silly=[brief2.txt, brief3.txt], dogs=[brief2.txt, brief3.txt], animals=[brief4.txt], birds=[brief4.txt], cute=[brief2.txt, brief3.txt], funny=[brief2.txt, brief3.txt]}

Update:and  [brief2.txt, brief3.txt, brief4.txt]
{love=[brief4.txt], cats=[brief2.txt, brief3.txt, brief4.txt], are=[brief2.txt, brief3.txt, brief4.txt], and=[brief2.txt, brief3.txt, brief4.txt], silly=[brief2.txt, brief3.txt, brief4.txt], dogs=[brief2.txt, brief3.txt], animals=[brief4.txt], birds=[brief4.txt], cute=[brief2.txt, brief3.txt, brief4.txt], funny=[brief2.txt, brief3.txt, brief4.txt]}

{love=[brief4.txt], cats=[brief2.txt, brief3.txt, brief4.txt], are=[brief2.txt, brief3.txt, brief4.txt], and=[brief2.txt, brief3.txt, brief4.txt], silly=[brief2.txt, brief3.txt, brief4.txt], dogs=[brief2.txt, brief3.txt], animals=[brief4.txt], birds=[brief4.txt], cute=[brief2.txt, brief3.txt, brief4.txt], funny=[brief2.txt, brief3.txt, brief4.txt]}

我真的不明白为什么在“update:are[brief1.txt,brief2.txt]”一行中,代码更新了这个arraylist值的所有map键。即使它会更新所有的钥匙的价值:为什么所有的钥匙除了狗?

提前感谢您的帮助!