我是Java的新手，目前正在夜间课程中学习它。我无法正确设置构造函数，以便将输入的值移动到数组中。我有下面的代码，似乎各个字段正确传递但数组没有填充，我无法弄清楚我做错了什么。我已经通过我的笔记，教科书和这里检查了。我可能只是盯着它看了太久了！
import java.util.Scanner;
public class Main {
static Scanner InOut = new Scanner(System.in);
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
// TODO code application logic here
//* Declare and initalize variables. Set maximum number of students to 6.
String surname = "", forename = "", course = "a", newCourse, tmpStu ="";
int firstMark = 0, secondMark = 0, thirdMark = 0, finalScore = 0,
option = 0, studentCount = 0, delNum, index = 0;
final int MAXSTUDENT = 6;
Student[] myClass = new Student[MAXSTUDENT];
//* Set class details for the constructor.
while (option != 6) {
//* Call the menu system to be displayed
option = menu();
switch (option) {
//* Checks the value return by the menu for the selected option
case 1:
//* Checks that the maximum number of students has not been exceeded.
if (studentCount >= MAXSTUDENT) {
System.out.println("Maximum number of student entered. \n\n");
menu();
} else {
//* Enter in the student details
InOut.nextLine(); /* ensures that the buffer is cleared*/
System.out.println("Enter student surname: ");
surname = InOut.nextLine();
System.out.println("Enter student forename: ");
forename = InOut.nextLine();
System.out.println("Enter 1st mark: ");
firstMark = InOut.nextInt();
System.out.println("Enter 2nd mark: ");
secondMark = InOut.nextInt();
System.out.println("Enter 3rd mark: ");
thirdMark = InOut.nextInt();
finalScore = 0;
//* Passes the entered paramaters to add the student details to the object class.
//* Increases the student counter by 1.
myClass[studentCount] = new Student(surname, forename, course, firstMark, secondMark, thirdMark, finalScore);
System.out.println(myClass[studentCount]);
studentCount++;
}
break;
case 2:
//* Enter in the student number to be deleted. Number is passed for deletion.
//* Reduces the number of student counter.
System.out.println("Delete which student?");
delNum = InOut.nextInt();
deleteStudent(delNum, studentCount);
studentCount--;
break;
case 3:
//* Allows for the course name to be updated.
InOut.nextLine(); /* ensures that the buffer is cleared*/
System.out.println("Enter new course: ");
newCourse = InOut.nextLine();
Student.setCourse(newCourse);
break;
case 4:
//* Display all details stored in the object class.
for (index = 0; index < studentCount; index = index + 1){
Student.displayDetails(index);
}
break;
case 5:
//* Input the surname of student and this name is passed to
//* display the details for this student only.
InOut.nextLine(); /* ensures that the buffer is cleared*/
System.out.println("Enter surname of student you want to search for: ");
String searchName = InOut.nextLine();
//* searchStudent(myClass, searchName, index, studentCount);
break;
case 6:
//* Exit program
System.out.println("End of program");
break;
default:
System.out.println("Invalid option");
}
}
}
public static int menu() {
//* Display menu options and returns selection.
System.out.println("****Student Menu****");
System.out.println("1. Add new student details");
System.out.println("2. Delete Student");
System.out.println("3. Change Course");
System.out.println("4. Display All Student Details");
System.out.println("5. Search Student by Name");
System.out.println("6. Exit");
System.out.println("\nInput an option:");
int option = InOut.nextInt();
return option;
}
public void addStudent(String surname, String forename, String course, int firstMark, int secondMark, int thirdMark, int finalScore)
//* Accepts passed paramaters of student details and adds them into the object class.
{
System.out.println(surname);
System.out.println(forename);
System.out.println(course);
System.out.println(firstMark);
System.out.println(secondMark);
System.out.println(thirdMark);
System.out.println(finalScore);
}
public static void deleteStudent(int delNum, int studentCount)
//* Accepts student array number to be deleted and displays details of all
//* students still stored.
{
//* int asize = myClass.length, index;
//* for (index = delNum +1; index < asize; index++)
//* {
//* myClass[index-1] = myClass[index];
//* }
//* studentCount --;
}
这是被调用的学生构造函数。我添加了一些显示语句，看看我是否能找到它出错的地方，但没有运气。我认为这可能与从“static void”main方法调用的构造函数有关。
import java.util.Scanner;
public class Student {
private String surname, forename;
private int firstMark, secondMark, thirdMark, finalScore, index;
private int stuCount = 0;
private final int NUMMARK = 3;
private static String course = "French";
Scanner InOut = new Scanner(System.in);
public Student(String surname, String forename, String course, int firstMark, int secondMark, int thirdMark, int finalScore)
{
System.out.println(surname);
this.surname = surname;
this.forename = forename;
this.course = course;
this.firstMark = firstMark;
this.secondMark = secondMark;
this.thirdMark = thirdMark;
finalScore = ((firstMark + secondMark + thirdMark)/ NUMMARK);
this.finalScore = finalScore;
}
public static void setCourse (String newCourse) {
course = newCourse;
}
private String getDetails()
//* Builds student details and returns them to be displayed.
{
String details = "Student Name: " + surname + ", " + forename +"\n";
details = details + "Course Name: " + course + "\n";
details = details + "Student's Marks: " + firstMark + ", " + secondMark + ", " + thirdMark + "\n";
details = details + "Final Mark: " + finalScore + "\n";
return details;
}
public static void displayDetails(int index)
//* Displays all student details that have been entered using the student counter
//* for the number of times to loop.
{
//* if (myClass[index] != null) {
//* System.out.println(myClass[index].getDetails());
//* }
}
}
答案 0 :(得分：3)
此
myClass[0] = new Student(surname, forename, course, firstMark, secondMark, thirdMark, finalScore);
studentCount++;
System.out.println(myClass[0]);
在上一个学生中添加每个新学生，你总是设置数组的第一个位置，它应该是这样的：
myClass[studentCount] = new Student(surname, forename, course, firstMark, secondMark, thirdMark, finalScore);
System.out.println(myClass[studentCount]);//BEFORE the counter increment
studentCount++;
旁注：
此代码：
System.out.println(myClass[studentCount]);
不会打印学生包含的信息。要打印它们，您必须覆盖toString类的Student方法，返回要打印的字符串
答案 1 :(得分：1)
您的代码没有任何严重问题。你只需要编辑它的一部分如下：
首先要查看Student类的getDeatails（）方法，你应该将其声明为 保护： 所以新版本如下
protected String getDetails()
{
String details = "Student Name: " + surname + ", " + forename + "\n";
details = details + "Course Name: " + course + "\n";
details = details + "Student's Marks: " + firstMark + ", " + secondMark + ", " + thirdMark + "\n";
details = details + "Final Mark: " + finalScore + "\n";
return details;
}
在第一种情况下你写的是好的。您只需使用适当的方法从数组中检索数据。所以使用以下代码：
//* Passes the entered paramaters to add the student details to the object class.
//* Increases the student counter by 1.
myClass[studentCount] = new Student(surname, forename, course, firstMark, secondMark, thirdMark, finalScore);
for(int i = 0;i<=studentCount;i++){
System.out.println(myClass[i].getDetails());
System.out.println("-----------------------");
}
studentCount++;
System.out.println("now the student count are: "+studentCount);
以下是案例4：
case 4:
//* Display all details stored in the object class.
System.out.println("studentcount:"+studentCount);
for (index = 0; index < studentCount; index = index + 1) {
System.out.println(myClass[index].getDetails());
System.out.println("---------------------");
}
break;