java - 使用 for 循环和用户输入将元素添加到 LinkedList

Question

我正在尝试使用 for 循环将元素添加到 LinkedList，每当我打印列表时，它只包含我的输入之一，并将其​​放在每个索引处。

我感觉问题出在我的 toString 方法或我的 Student 构造函数上，但似乎无法弄清楚。

感谢任何和所有帮助。谢谢!

 import java.util.*;

public class Student {

    private static String name;
    private static String address;
    private static double GPA;
    static LinkedList<Student> stu = new LinkedList<Student>();
    static Scanner scanner = new Scanner(System.in);


    public Student(String name, String address, double GPA) {
        Student.name = name;
        Student.address = address;
        Student.GPA = GPA;
    }

    public String getName() {
        return Student.name;
    }

    public String getAddr() {
        return Student.address;
    }

    public double getGPA() {
        return Student.GPA;
    }

    public static void main(String [] args) {
        for (int i = 0; i <= 2; i++) {
            System.out.println("Enter the student's name: ");
            name = scanner.next();
            System.out.println("Enter the student's address: ");
            address = scanner.next();
            System.out.println("Enter the student's GPA: ");
            GPA = scanner.nextDouble();
            stu.addLast(new Student(name, address, GPA));
        }
        System.out.println(stu);
    }

    @Override
    public String toString() {
    String str = "Name: " + getName() + "\nAddress: " + getAddr() + "\nGPA: " + getGPA()+ "\n\n";
    return str;
    }
}

控制台

Enter the student's name: 
Jim
Enter the student's address: 
111Ave
Enter the student's GPA: 
2.3
Enter the student's name: 
Joe
Enter the student's address: 
222Ave
Enter the student's GPA: 
3.0
Enter the student's name: 
Jack
Enter the student's address: 
333Ave
Enter the student's GPA: 
3.4
[Name: Jack
Address: 333Ave
GPA: 3.4

, Name: Jack
Address: 333Ave
GPA: 3.4

, Name: Jack
Address: 333Ave
GPA: 3.4

]

Answer 1

属性name , address ，和GPA是static ，这意味着可以从您创建的所有学生对象访问它们。因此，当您创建一个新的学生对象并调用它的构造函数时，您会更改 name 的值。 , address ，和GPA对于您之前创建的所有其他学生对象。

要解决您的问题，您需要删除 static name 声明中的关键字, address ，和GPA .

现在剩下的就是更改访问变量的方式。请注意您过去如何使用 Student.name每当您想使用属性name时？这仅在 name 时有效是静态的“又名 name 对于所有 Student 都是相同的”。我们现在要使用name 当前学生而不是所有学生，所以我们应该使用 this.name而不是Student.name 。同样改变Student.GPA至this.GPA和Student.address至this.address .

此外，您不能只使用属性 name , address ，和GPA在你的 main 中没有对象“因为它们不再是 static”，所以你需要声明 name , address ，和GPA在 main 中，请注意这些变量与 Student 中的变量属性无关。类(class)。请参阅此代码以更好地理解，对于我糟糕的解释感到抱歉。

import java.util.*;

public class Student {

    private String name;
    private String address;
    private double GPA;
    static LinkedList<Student> stu = new LinkedList<Student>();
    static Scanner scanner = new Scanner(System.in);


    public Student(String name, String address, double GPA) {
        this.name = name;           //this.name instead of Student.name
        this.address = address;     //this.address instead of Student.address
        this.GPA = GPA;             //this.GPA instead of Student.GPA
    }

    public String getName() {
        return this.name;           //similarly
    }

    public String getAddr() {
        return this.address;        //similarly
    }

    public double getGPA() {
        return this.GPA;            //similarly
    }

    public static void main(String [] args) {
        for (int i = 0; i <= 2; i++) {
            System.out.println("Enter the student's name: ");

            //notice here. "name" can be changed to anything, "sname" for example
            //this variable is just to store the input, it's not related to the name
            //attribute in the class
            String name = scanner.next();
            System.out.println("Enter the student's address: ");

            //same goes for address and GPA
            String address = scanner.next();
            System.out.println("Enter the student's GPA: ");
            double GPA = scanner.nextDouble();

            //use the input taken above to create a new student by calling the constructor
            stu.addLast(new Student(name, address, GPA));
        }
        System.out.println(stu);
    }

    @Override
    public String toString() {
        String str = "Name: " + getName() + "\nAddress: " + getAddr() + "\nGPA: " + getGPA()+ "\n\n";
        return str;
    }
}