java - 如何访问不同类中的ArrayList

Question

我有一个 Main.java 文件，在这个类中我创建了一个学生对象的 ArrayList。我想将这些对象传递给另一个名为 IntroSentenceHigh 的包中的另一个类。

这是我的 Main.java 文件中的代码:

public class Main 
{

public static void main(String[] args) 
{
    ArrayList<Student> StudentList = new ArrayList<Student>();
    // Student details --- Name, Year Level, Gender, Average Test Score, Exam Score, Classwork, Homework, Practical Work, Behaviour
    Student student1 = new Student("Bob", 12, "M", 100, 100, 1, 1, 1, 1);
    Student student1 = new Student("John", 12, "M", 100, 100, 1, 1, 1, 1);

    StudentList.add(student1);
    StudentList.add(student2);

    // Loop through all student data in the array
    for (int i = 0; i < StudentList.size(); i++)
    {
        System.out.println(StudentList.get(i).viewStudentInfo());
    }

    IntroSentenceHigh introSentenceHigh = new IntroSentenceHigh();

我有一个 Student.java 类，其中包含以下内容:

public class Student 
{
    private String name;
    private int yearLevel;
    private String gender;

    // Student marks
    private int testAverage;
    private int exam;

    // Other student data
    private int classwork;
    private int homework;
    private int practicalWork;
    private int behaviour;

    public Student(String name, int yearLevel, String gender, int testAverage, int exam, int classwork,
               int homework, int practicalWork, int behaviour)
    {
        this.name = name;
        this.yearLevel = yearLevel;
        this.gender = gender;
        this.testAverage = testAverage;
        this.exam = exam;

        // Student's are given scores from 1 to 3. 
        // 1 is best, 3 is worst
        this.classwork = classwork;
        this.homework = homework;
        this.practicalWork = practicalWork;
        this.behaviour = behaviour;
    }

    public String getName()
    {
        return name;
    }

    public int getYearLevel()
    {
        return yearLevel;
    }

    public String getGender()
    {
        return gender;
    }

    public int getTestAverage()
    {
        return testAverage;
    }

    public int getExam()
    {
        return exam;
    }

    public int getClasswork()
    {
        return classwork;
    }

    public int getHomework()
    {
        return homework;
    }

    public int getPracticalWork()
    {
        return practicalWork;
    }

    public int getBehaviour()
    {
        return behaviour;
    }

    public String viewStudentInfo()
    {
        String studentInfo;
        studentInfo = "Student name: " + getName() + "\n" + 
                      "Year: " + getYearLevel() + "\n" +
                      "Gender: " + getGender() + "\n" + 
                      "Test Average: " + getTestAverage() + "\n" +
                      "Exam result: " + getExam()+ 
                      "\n";
        return studentInfo;
    }
}

最后，我有一个 IntroSentenceHigh.java 类，其中包含以下代码:

public class IntroSentenceHigh 
{

private String introSentenceHigh1 = "Student statement 1";
private String introSentenceHigh2 = "Student statement 2";

public String getIntroSentenceHigh1()
{
    return introSentenceHigh1;
}

public String getIntroSentenceHigh2()
{
    return introSentenceHigh2;
}

基本上，我想在 IntroSentenceHigh 类中访问学生姓名和性别，但我不知道如何从创建 ArrayList 的 Main.java 类中获取它。我寻找同一主题的答案，但由于我是初学者，我不知道如何修改我的代码以使其工作。

任何帮助都会很棒。谢谢!

Answer 1

有很多方法可以完全满足您的要求，最简单的可能是使用参数化构造函数。这意味着向 IntroSentenceHigh 类添加一个 ArrayList 参数(顺便说一下，这不是一个非常直观的名称)，并在该类中设置一个等于 ArrayList 的全局变量。这是一种方法:

public Class IntroSentenceHigh { 

private ArrayList<Student> studentList; 

public IntroSentenceHigh(ArrayList<Student> studentList) { 
  this.studentList = studentList
}

现在，您的全局变量 StudentList 包含您在 Main 中创建的 Students ArrayList。然后，您可以使用在 Student 类中声明的 getter 来接收所需的信息。一个例子是:

String aName = studentList.get(0).getName();

记住在创建 IntroSentenceHigh 实例时添加 ArrayList 参数(幸运的是，编译器也会提醒您该要求​​；))