一个 ArrayList 包含两个元素，如何只返回 String 元素？

Question

我对 Java 还很陌生，但我觉得这是一项简单的任务。这个数组列表有两个元素……名字和分数。我想编写一个方法来打印列表中所有名称的列表，而不是分数。我知道我之前已经这样做了，我只是不记得如何大声笑

import java.util.ArrayList;
/**
 * Print test scrose and student names as well as he average for the class.
 */
public class TestScores {
  private ArrayList<Classroom> scores;
  public int studentScores;

  /**
   * Create a new ArrayList of scores and add some scores
   */
  public TestScores() {
    scores = new ArrayList<Classroom>();
  }

  /**
   * Add a new student and a new score.
   */
  public void add (String name, int score) {
    scores.add(new Classroom(name, score));
    if(score > 100){
      System.out.println("The score cannot be more than 100");
    }    
  }

  /**
   * Return all the student names.
   */
  public void printAllNames() {//this is the method.
    for (Classroom s : scores){
      System.out.println(scores.get(name));
    }
  }
}

和课堂：

import java.util.ArrayList;
/**
 * This class creates the names and scores of the students
 */
public class Classroom {
  public int score;
  public String name;

  /**
   * Constructor for the Class that adds a name and a score.
   */
  public Classroom(String aName, int aScore) {
    score = aScore;
    name = aName;
  }

  /**
   * Return the name of the students
   */
  public String returnName() {
    return name;
  }

  /**
   * Return he scores
   */
  public int returnScore() {
    return score;
  }
}

Answer 1

public void printAllNames() {//this is the method.
  for (Classroom s : scores){
    System.out.println(s.returnName());
  }
}

您的问题应该是精确的，您的列表不包含 2 个元素 - 名称和分数 - 而是包含名称和分数的多个 Classroom 对象。

使用 Java 8 流的替代答案：

scores.stream().map(c -> c.returnName()).forEach(System.out::println);