如何在Java中的对象数组中保留一个对象

Question

我不知道如何问这个问题。我必须编写一个具有 2 个类的程序：一个存储数据，一个调用显示数据。数据是学生的姓名和他/她的4门课程的名称。但我必须把它放在一个循环中，让用户输入至少 3 条记录。如果用户没有输入学生的姓名（或姓名 = 空白），则退出循环并显示输入的信息。

例子：

John Doe MATH 101 ENGL 101 READ 101 COMP 101
Jane Doe PHYS 101 CHEM 101 PSYC 101 ACCT 101
Mary Doe PHED 101 HIST 101 CALC 101 POLS 101

我要做的是让每个学生记录一个对象并将这 3 个对象存储在一个对象数组中然后显示它。

下面是我的代码：

import java.util.Scanner;
public class UserInterface {
    public static void main(String[] args) {
    //Create a scanner
    Scanner input = new Scanner(System.in);

    //Create an object from Business class
    Business b = new Business();

    //Declare variables
    final int NUMBER_OF_COURSES = 4;
    String[] coursesName = new String[4];
    Business[] businessArray = new Business[3]; //Declare a array of objects

    for (int counter = 0; counter < businessArray.length; counter++) {

    //Prompt user to input name
    System.out.println("Enter student's name: ");
    b.setName(input.nextLine());

    for (int i = 0; i < NUMBER_OF_COURSES; i++) {
    System.out.println("Enter " + b.getName() + "'s course number " + (i + 1));
    coursesName[i] = input.nextLine();
    }//end of for(i)-loop

    b.setCourses(coursesName);

    businessArray[counter] = b;

    System.out.println(businessArray[counter]); //Here it display correctly for each round

    }//End of for(counter)-loop

    for (int pa = 0; pa < businessArray.length; pa++)
        System.out.println(businessArray[pa]);         //but here it displays 3 records of the last entry
                                                        //so my question is how do I retain each entry in its own object and 
                                                     //adds it to the array of objects? 
                                                     //I know that b gets overwrite by the last data entered because
                                                    //it is just a pointer to that object.  

    input.close();

    }//End of main method

}//End of class UserInterface


The other class:

public class Business {

    //Declare variables
    private String name;
    private String[] courses = new String[4];

    //Default Constructor
    public Business(){

    }

    //getter for student's name
    public String getName() {
        return name;
    }

    //setter for student's name
    public void setName(String name) {
        this.name = name;
    }

    //getter for courses' name
    public String[] getCourses() {
        return courses;
    }

    //setter for courses' name
    public void setCourses(String[] courses) {
        this.courses = courses;
    }

}//End of class Business

我知道我的代码不好。但是我需要为这个 Business 类中的每个变量设置 getter 和 setter。

Answer 1

将您创建的 Business 对象移动到 for 循环中：

for (int counter = 0; counter < businessArray.length; counter++) {
    Business b = new Business();
    // ...
}

现在，数组中的每个条目都指向同一个对象，因此您正在重复覆盖其中的值。将创建移动到循环中意味着您将为数组的每个插槽拥有不同的对象。

Answer 2

String retainCourse(int pointer){
    return this.courses[pointer];
}

将此功能添加到您的业务类。

您应该覆盖该类的.toString() 方法以获得预期的结果。

在 for 循环中，更好的做法是获取当前对象并将其设置为强制转换为确切类的临时变量！ Business current = (Business) businesses[i];