我从arraylist获取内存地址，需要信息

  • Z时代
  • 2024-01-10
  • 分类：问答

我正在获取一个文本文件并填充一个arraylist。为了测试文件，我在继续之前将其打印出来。我只能从文件中看到内存地址，而不能看到实际信息。有什么简单的东西，也许很明显我想念吗？

public class TriviaQuestion {
private String player;
private String category;
private String question;
private String answer;
private int score = 0;
/**
 * 
 */
public TriviaQuestion() {
    player = "unknown";
    category = "unknown";
    question = "unknown";
    answer = "unknown";
    score = 0;
}
public TriviaQuestion(String category, String question, String answer){
}
public TriviaQuestion(String player, String category, String question,
        String answer, int score) {
    super();
    this.player = player;
    this.category = category;
    this.question = question;
    this.answer = answer;
    this.score = score;
}
/**
 * @return the player
 */
public String getPlayer() {
    return player;
}
/**
 * @param player the player to set
 */
public void setPlayer(String player) {
    this.player = player;
}
/**
 * @return the category
 */
public String getCategory() {
    return category;
}
/**
 * @param category the category to set
 */
public void setCategory(String category) {
    this.category = category;
}
/**
 * @return the question
 */
public String getQuestion() {
    return question;
}
/**
 * @param question the question to set
 */
public void setQuestion(String question) {
    this.question = question;
}
/**
 * @return the answer
 */
public String getAnswer() {
    return answer;
}
/**
 * @param answer the answer to set
 */
public void setAnswer(String answer) {
    this.answer = answer;
}
/**
 * @return the score
 */
public int getScore() {
    return score;
}
/**
 * @param score the score to set
 */
public void setScore(int score) {
    this.score = score;
}
}

测试员

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Scanner;
public class TriviaQuestionTester {
/**
 * @param args
 */
public static void main(String[] args) throws IOException {
     File triviaFile = new File("trivia.txt");
    Scanner triviaFile1 = new Scanner(triviaFile);
    String lastKnownCategory = "";
    ArrayList<TriviaQuestion> myList = new ArrayList<TriviaQuestion>();
    while (triviaFile1.hasNextLine()){
        String currentLine = triviaFile1.nextLine();
        if (!currentLine.isEmpty()) {
            TriviaQuestion currentQuestion = new TriviaQuestion(currentLine,     currentLine, currentLine);
            if (currentLine.endsWith("?")) {
                currentQuestion.setCategory(lastKnownCategory);
                currentQuestion.setQuestion(currentLine);
                currentQuestion.setAnswer(triviaFile1.nextLine());
            } else {
                currentQuestion.setCategory(currentLine);
                currentQuestion.setQuestion(triviaFile1.nextLine());
                currentQuestion.setAnswer(triviaFile1.nextLine());
                lastKnownCategory = currentLine;
            }
            myList.add(currentQuestion);
        }
    }
    triviaFile1.close();
    System.out.println(myList);
}
}

回答：

有什么简单的东西，也许很明显我想念吗？

是的-

你没有覆盖toString的TriviaQuestion，所以你得到的默认实现Object：

Object类的toString方法返回一个字符串，该字符串包括该对象是其实例的类的名称，符号字符“

@”以及该对象的哈希码的无符号十六进制表示形式。换句话说，此方法返回的字符串等于：

getClass().getName() + '@' + Integer.toHexString(hashCode())

只需将其添加到TriviaQuestion：

@Override public String toString() {
    return "Player: " + player + "; Category: " + category 
        + "; Question: " + question + "; Answer: " + answer
        + "; Score: " + score;
}

（或String.format在方法内使用以执行相同的操作。）

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