[英]Why won't my array pass to the other class?
我看過類似的例子或從另一個類調用數組的其他程序,似乎我已經以正確的方式完成了它,但我仍然遇到錯誤。 這是存儲數組的地方:
import java.util.Scanner;
public class DriverProgram {
public static int[] IDs = new int[10];
public static String[] names = new String[10];
public static double[] grades = new double[10];
public static int i = 0;
static Student call = new Student();
public static void main(String[] args){
call = new Student();
Scanner command = new Scanner(System.in);
System.out.println("Please Enter a command(i, r, s, or d): ");
while(command.hasNext()){
char command1 = command.next().charAt(0);
if(command1 == 'i'){
call.AddToArray(IDs[], names[] , grades[], i);
}else if(command1 == 'r'){
call.RemoveFromArray(int [] IDs, String [] names,double [] grades, int i);
}else if(command1 == 's'){
call.SortArray(int [] IDs, String [] names,double [] grades, int i);
}else if(command1 == 'd'){
call.DisplayArray(int [] IDs, String [] names,double [] grades, int i);
}else if(command1 == 'z') {
break;
}
else System.out.println("Invalid command enter a valid command next time.");
System.out.println("Please Enter a command(i, r, s, or d) or z to finish: ");
}
}
這就是我試圖將數組調用為:
import java.util.Scanner;
public class Student {
public static void AddToArray(int[] IDs, String[] names, double[] grades, int i) {
if (i >= 10) {
System.out.println("You have already inputted 10 students please delete one first.");
} else {
Scanner readin = new Scanner(System.in);
Scanner readinname = new Scanner(System.in);
Scanner readingrade = new Scanner(System.in);
System.out.println("Please enter student ID: ");
IDs[i] = readin.nextInt();
System.out.println("Please enter student name: ");
names[i] = readinname.nextLine();
System.out.println("Please enter student grade: ");
grades[i] = readingrade.nextDouble();
System.out.println(IDs[i] + " " + names[i] + " " + grades[i]);
i++;
for (int j = 0; j < i; j++) {
if (IDs[j] == IDs[i]) {
System.out.println("This student has already been entered.");
}else{
System.out.println("The student has been added");
break;
}
}
}
}
我不確定為了調用這些數組我還需要什么或缺少什么。
call.AddToArray(IDs[], names[] , grades[], i);
應該替換為
call.AddToArray(IDs, names , grades, i);
PS設計筆記
Student
只有static
方法,所以這是實用類,不應允許創建實例call.AddToArray()
和其他static
方法應該被稱為Student.AddToArray()
array
不是正確的數據結構,您可以在其中添加或刪除元素。 有更合適的數據結構,如List
或Map
。Scanner
實例。 這就是DriverProgram
樣子。
public class DriverProgram {
public static void main(String[] args) {
Map<Integer, Student> students = new HashMap<>();
Scanner scan = new Scanner(System.in);
while (scan.hasNext()) {
System.out.println("Please Enter a command [1-5]:");
System.out.println("1. add new student");
System.out.println("2. remove existed student");
System.out.println("3. sort existed students by grades desc");
System.out.println("4. show existed students");
System.out.println("5. exit");
System.out.print("> ");
int menu = scan.nextInt();
if (menu == 1)
addStudent(scan, students);
else if (menu == 2)
removeStudent(scan, students);
else if (menu == 3)
sortStudents(students);
else if (menu == 4)
showStudents(students);
else if (menu == 5)
break;
System.err.println("Unknown command. Try again");
}
}
private static void addStudent(Scanner scan, Map<Integer, Student> students) {
if (students.size() == 10) {
System.err.println("You have already inputted 10 students please delete one first.");
return;
}
System.out.print("Please enter student ID: ");
int id = scan.nextInt();
if (students.containsKey(id)) {
System.err.println("This student with this id has already been entered.");
return;
}
System.out.print("Please enter student name: ");
String name = scan.nextLine();
System.out.print("Please enter student grade: ");
double grade = scan.nextDouble();
students.put(id, new Student(id, name, grade));
}
private static void removeStudent(Scanner scan, Map<Integer, Student> students) {
}
private static void sortStudents(Map<Integer, Student> students) {
}
private static void showStudents(Map<Integer, Student> students) {
}
public static final class Student {
private final int id;
private final String name;
private final double grade;
public Student(int id, String name, double grade) {
this.id = id;
this.name = name;
this.grade = grade;
}
}
}
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