我有一個String []數組列表以家庭作業，

Question

這裏是我寫的代碼：

public class TestCourse { public static void main(String[] args) { 
    Course course1 = new Course("Data Structures"); 
    Course course2 = new Course("Database Systems"); 

    course1.addStudent("Peter Jones"); 
    course1.addStudent("Brian Smith"); 
    course1.addStudent("Anne Kennedy"); 

    course2.addStudent("Peter Jones"); 
    course2.addStudent("Steve Smith"); 

    System.out.println("Number of students in course1: " 
     + course1.getNumberOfStudents()); 
    String[] students = course1.getStudents(); 
    for (int i = 0; i < course1.getNumberOfStudents(); i++) 
     System.out.print(students[i] + ", "); 

    System.out.println(); 
    System.out.print("Number of students in course2: " 
     + course2.getNumberOfStudents()); } } 

import java.util.ArrayList; public class Course { 

    private String courseName; 
    private ArrayList<String> students = new ArrayList<>(); 
    private int numberOfStudents; 

    public Course(String courseName) { 
     this.courseName = courseName; 
    } 
    public void addStudent(String name) { 
     students.add(name); 
     numberOfStudents ++; 
    } 
    public ArrayList getStudents() { 
     return students; 
    } 
    public int getNumberOfStudents() { 
     return numberOfStudents; 
    } 

    public String getCourseName() { 
     return courseName; 
    } 
    public void dropStudents(ArrayList students) { 
     this.students = students; 
     students.remove(students); 
     numberOfStudents --; 
    } } 

我在 String[] students = course1.getStudents();一個錯誤的測試過程。

我試圖把數組列表，但它沒有工作..

Answer 1

首先，您傳回raw type。所以解決。喜歡的東西，

public ArrayList<String> getStudents() { 
    return students; 
} 

接下來，你可以調用List.toArray(T[])像

String[] students = course1.getStudents().toArray(new String[]{}); 

或直接使用List，像

List<String> students = course1.getStudents(); 
for (String student : students) { 
    // Do something with each student. 
}