Question

我一直在搜索所有地方，但是找不到答案。

我正在尝试创建一个ArrayList来在用户定义的类中存储10个等级，因此我可以在Client类中调用它，并使用Scanner（System.in）输入等级，然后将它们一起输出，但是我不知道是否有可能这样做，而且我到处都在寻找答案。请帮忙。

到目前为止，这是我定义的用户定义类

import java.util.ArrayList;

public class Student {

private String student;
private String courseName;
private double grade;
private double avg;
private double total;
private double max;
private double min;

//Constructor w/o arguments
public Student() {
    this.student = "";
    this.courseName = "";
    this.grade = 0.0;
}

//Constructor with arguments
public Student(String student, String courseName, double grade, double avg, double total, double max, double min) {
    this.student = student;
    this.courseName = courseName;
    this.grade = grade;
}

//Getters
public String getStudent(){
    return this.student;
}
public String getCourseName() {
    return this.courseName;
}


//Setters
public void setStudent(String student) {
    this.student = student;
}
public void setCourseName(String courseName) {
    this.courseName = courseName;
}


//Returns average off the 10 grades
public double calculateAvg() {
    total += grade; //add all grades for average
    avg = total / 10;
    return avg;
}

//Highest Grade
public double highGrade() {
    return max = Math.max(grade, max);
}
//Lowest Grade
public double lowGrade() {
    return min = Math.min(grade, min);
}

ArrayList<Student>listGrades = new ArrayList<Student>();

Answer 1

不确定要了解什么，但是可以做到：

class Student {
  private final List<Double> grades = new ArrayList<>(10);
  private final String name;
  // Constructor, getters & setters omitted. 
}

// ..
Student student = // ...
for (int i=0; i<10; i++) {
    System.out.println("Please enter the "+(i+1)+"th grade:");
    student.getGrades().add(scanner.nextDouble());
}
// ..
Student student = // ...
student.getGrades().forEach(System.out::println);

注意，这不是最佳方法。您可以在https://codereview.stackexchange.com/社区中搜索“学生成绩java” ，以查找有关类似问题的大量评论。

Answer 2

在构造函数或其他方法中将其初始化： [https://www.geeksforgeeks.org/initialize-an-arraylist-in-java/][1]

Answer 3

您应该尝试这样的事情。

public static void main(String[] args) {
            System.out.println("Enter number of Students :");
            Scanner scanner = new Scanner(System.in); 
            Student s=new Student("gagan","Math",0.0d,0.0d, 0.0d, 0.0d,0.0d);
            s.listGrades.add(s);

            for(Student s1:s.listGrades) {
                System.out.println("Enter Grade for student"+s.getStudent()+": ");
                s1.setGrade(scanner.nextDouble());
            }
            scanner.close();


        }

在用户定义的类Java中创建ArrayList

3 个答案: