これは私が持っている Student クラスで、名前、学年、ID 番号を持つ学生を作成します。Student は TreeMap のキーとして使用され、学生の成績は値として使用されます。私はComparableを実装しているのでcompareToを書きましたが、最初の学生に入るとこのエラーがポップアップします:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 1
at Student.<init>(Student.java:25)
at Main.main(Main.java:50)
Java Result: 1
学生の名前を文字列 [] に分割したことが原因だと思いますが、姓名を呼び出す行と、名前を分割する行をテストしましたが、すべて意図したとおりに機能しているようですただし、compareTo で呼び出される場合を除きます。
どんな助けでも大歓迎です。
public class Student implements Comparable<Student>{
private String name, grade, first, last;
private String[] stuName;
private int id;
/**
* Constructs a new Student with a name, ID Number, and a grade.
* @param n name
* @param i ID Number
* @param g grade
*/
public Student(String n, int i, String g){
name = n;
id = i;
grade = g;
stuName = n.split(" ");
first = stuName[0];
last = stuName[1];
}
/**
* Compares Students. First by last name, then by first if the last names
* are the same. If the first names are also the same, the students are
* compared by their ID Numbers.
* @return the value upon comparing the proper property of the Student
*/
@Override
public int compareTo(Student other){
if (last.equals(other.getLast())){
if (first.equals(other.getFirst())){
return id - other.getID();
}else
return first.compareTo(other.getFirst());
}
return last.compareTo(other.getLast());
}
/**
* Changes the student's current grade.
* @param g new grade
*/
public void changeGrade(String g){
grade = g;
}
/**
* Returns student's name.
* @return name
*/
public String getName(){
return name;
}
/**
* Returns student's first name.
* @return first name
*/
public String getFirst(){
return first;
}
/**
* Returns student's last name.
* @return last name
*/
public String getLast(){
return last;
}
/**
* Returns the student's grade.
* @return grade
*/
public String getGrade(){
return grade;
}
/**
* Returns the student's ID Number
* @return id number
*/
public int getID(){
return id;
}
テスター：
public class Main {
public static void main(String[] args) throws InterruptedException{
Map<Student, String> students = new TreeMap();
Scanner in = new Scanner(System.in);
System.out.println("How many students do you want to add?");
int numStudents = in.nextInt();
String name, grade;
int id;
for (int i = 1; i < numStudents; i++){
System.out.println("Name of student " + i + "?");
name = in.nextLine();
in.nextLine();
System.out.println("Grade of " + i + "?");
grade = in.nextLine();
System.out.println("ID Number of " + i + "?");
id = in.nextInt();
Student s = new Student(name, id, grade);
students.put(s, s.getGrade());
}
System.out.println("How many students do want to remove");
int remStudents = in.nextInt();
for (int i = 0; i < remStudents; i++){
System.out.println("ID?");
int remID = in.nextInt();
for (Student s : students.keySet()){
if (s.getID() == remID){
students.remove(s);
}
}
}
System.out.println("How many grades do you want to change?");
int changeGrades = in.nextInt();
for (int i = 0; i < changeGrades; i++){
System.out.println("ID?");
int foo = in.nextInt();
System.out.println("New grade?");
String newGrade = in.nextLine();
for (Student s : students.keySet()){
if (s.getID() == foo){
s.changeGrade(newGrade);
}
}
}
String printout = "";
for (Student s : students.keySet()){
printout += s.getLast() + ", " + s.getFirst() + " (" + s.getID() + "): " + s.getGrade() + "\n";
}
System.out.println(printout);
}
}