java - 为什么我的程序无法正确检查列表是否已包含特定字符？

Question

我正在创建一个类，它解析文件中的所有字符并查找每个字母出现的次数。

第一步，当我浏览文件添加字符时，我会检查字符列表是否已包含我所在的特定字符。如果不存在，则将其添加到列表中，出现次数值为 1；如果已包含该列表，则将出现次数增加 1。

但是，我的下面的代码无法正确确定列表是否已包含特定字符。

我正在使用 ArrayList，并且我知道我必须重写 CharProfile 类中的 equals 方法(我确实这样做了)，以便 contains() 使用的 equals() 方法正常工作。

重写 CharProfile 中的 equals 方法:

    @Override
    public boolean equals(Object o) {
        if (this.character == ((Character)o)) {
            return true;
        }
        else {
            return false;
        }
    }

代码:

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

public class HuffmanCoder {
    public static void main(String[] args) throws IOException {
        Scanner keyboard = new Scanner(System.in);

        System.out.print("Please enter the name of the file to be read from: ");
        String fileName = keyboard.nextLine();

        File file = new File(fileName);
        Scanner inputFile = new Scanner(file);

        int charCount = 0;
        ArrayList<CharProfile> charOccurrences = new ArrayList<CharProfile>();

        while (inputFile.hasNext()) {
            // Grabs the next word in the file and converts it into a char array
            String word = inputFile.next();
            char[] wordArray = word.toCharArray();

            // Parses the word on a char-by-char basis
            for (int i = 0; i < wordArray.length; i++) {
                if (wordArray[i] != ' ') {
                    charCount++;

                    // Constructs the list of chars and their respective number of occurrences
                    if (!charOccurrences.contains(wordArray[i])) {
                        charOccurrences.add(new CharProfile(wordArray[i]));
                    }
                    else {
                        for (int j = 0; j < charOccurrences.size(); j++) {
                            if (charOccurrences.get(j).getCharacter() == wordArray[i]) {
                                charOccurrences.get(j).incremementOccurrences();
                                break;
                            }
                        }
                    }
                }
            }
        }

        // Figure out each char's probability
        for (int i = 0; i < charOccurrences.size(); i++) {
            System.out.println(charOccurrences.get(i).getCharacter());
        }
    }   
}

完整的 CharProfile 类:

public class CharProfile {
    private char character;
    private int occurrences;
    private double probability;

    public CharProfile(char character) {
        this.character = character;
        occurrences = 1;
    }

    public void incremementOccurrences() {
        occurrences++;
    }

    public char getCharacter() {
        return character;
    }

    public void setCharacter(char character) {
        this.character = character;
    }

    public int getOccurrences() {
        return occurrences;
    }

    public void setOccurrences(int occurrences) {
        this.occurrences = occurrences;
    }

    public double getProbability() {
        return probability;
    }

    public void setProbability(double probability) {
        this.probability = probability;
    }

    public boolean equals(char character) {
        if (this.character == character) {
            return true;
        }
        else {
            return false;
        }
    }

    @Override
    public boolean equals(Object o) {
        if (this.character == ((Character)o)) {
            return true;
        }
        else if (this.character == ((Character)o).charValue()) {
            return true;
        }
        else {
            return false;
        }
    }
}

问题简而言之:在检查列表是否已包含该字符时，它似乎总是返回 false，而不是返回 true，导致文件中的每个字符都被添加到列表中，而它应该只是唯一的字符。

Answer 1

这只是比较对象引用是否相同，并且实例是 Character 而不是 CharProfile。

@Override
public boolean equals(Object o) {
    if (this.character == ((Character)o)) {
        return true;
    }
    else {
        return false;
    }
}

您需要更改 equals 方法以接受 CharProfile 实例并比较其中的字符值，如下所示:

@Override
public boolean equals(Object o) {
    if(this.character == ((CharProfile)o).getCharacter()) {
        return true;
    }else {
        return false;
    }
}

编辑:您的 equal 方法没有被调用，因为您将 char 传递给 contains 方法。

请将其更改为:

         // Constructs the list of chars and their respective number of occurrences
         CharProfile charProfile = new CharProfile(wordArray[i]);
         if (!charOccurrences.contains(charProfile)) {
              charOccurrences.add(charProfile);
         }