Question

Hi, I’m very new to java and I’m currently trying to create a student name and mark menu but I’m having trouble with my add method, I think it’s something to do with my Arrays but I can’t figure it out, any help would be appreciated.

Below is my unitResult method

public class UnitResults 
{
    private String unitTitle;
    private String [] fName;
    private String [] surname;
    //private String [] UnitResults;
    private int [] Marks;
    private int Mark;

    private int pointer ;

    private static String course = "HND Computing"; 

    public UnitResults(int Size,String title)
    {            
        this.fName = new String [Size];
        this.surname = new String [Size];
        this.Marks = new int [Size];
        pointer = 0;

        fName[pointer] = "Daniel";
        surname[pointer] = "Scullion";

        Marks[pointer] = 60;
        unitTitle  = title;

        pointer ++;
    }

    public Boolean add( String tempfName, String tempsName, int newGrade)
    { 
        if (pointer == fName.length)
        {
            System.out.println("The Students Database is full");
            return false;
        }

        else
        {
            fName [pointer] = tempfName;
            surname [pointer]  = tempsName;
            Marks[pointer] = newGrade;

            pointer ++;
            return true;
        }
    }// end Add

but when I try to add this using a menu system below

int option = 0;
option = menuSystem();

while (option != 6)
{
    System.out.println("");
    switch(option)
    {
    case 1:
        System.out.println(" Please Enter The Students First Name");
        String tempfName = keyb.nextLine();

        System.out.println("Please Enter The Students Last Name");
        String tempsName = keyb.nextLine();

        System.out.println(" Please Enter The Students Mark");
        int newGrade = keyb.nextInt();
        myUnit.add(tempfName, tempfName,newGrade);   

        break;

When I enter my option 1 the output that I get is :

Please Enter The Students First Name

Please Enter The Students Last Name

Any ideas what’s wrong here been searching for a long time, probably something simple but I’ve no idea :/

Edit: below is my menu class

import java.util.Scanner;

public class MenuResults {
    static Scanner keyb = new Scanner(System.in);

    public static int menuSystem()
    {
        System.out.println("*********************************");
        System.out.println("                                 ");
        System.out.println("1.Add New Student");
        System.out.println("2.Display Students Details");
        System.out.println("3.Delete a Students");
        System.out.println("4.Update Student Details");
        System.out.println("5.Sort Students By Mark");
        System.out.println("6.Sort Students By Surname");
        System.out.println("7.Search For A Student");
        System.out.println("                                 ");
        System.out.println("**********************************");

        System.out.print("\n Enter choice:");
        int option = keyb.nextInt();
        return option;
    }

    public static void main(String[] args) {
        UnitResults myUnit = new UnitResults(3, "Java");

        int option = 0;
        option = menuSystem();

        while (option != 6)
        {
            System.out.println("");
            switch(option)
            {
            case 1:                   

                System.out.println(" Please Enter The Students First Name");
                String tempfName = keyb.nextLine();

                System.out.println("Please Enter The Students Last Name");
                String tempsName = keyb.nextLine();

                System.out.println(" Please Enter The Students Mark");
                int newGrade = keyb.nextInt();
                myUnit.add(tempfName, tempsName,newGrade);   

                break;
            case 2:
                myUnit.display();
                break;
            case 3:

                break;
            case 4:

                break;
            case 5:

            case 6:

                break;
            default:
                System.out.println(" Invalid Entry");
            }//end switch 
        }
    }
}

There is my whole menu class as asked for.

EDIT: when I forget the user input and hard input it using: myUnit.add("John","tommy",12);

I get "Student Database is full" about one hundred times..

Answer 1

Wild guess, when you use your menu and type 1 then ENTER a carriage return (\n) for the ENTER is still present in your Scanner after nextInt() is called.

So next call to readLine() will use the \n (remaining ENTER) for the line and will not wait for user input.

Possible correction:

public static int menuSystem()
{
    final Scanner keyb = new Scanner(System.in);
    // ...
}

public static void main(String[] args) {
    final UnitResults myUnit = new UnitResults(3, "Java");
    int option = menuSystem();
    while (option != 6) {
        final Scanner keyb = new Scanner(System.in);
        // ...
        option = menuSystem();
    }
}

And removal of the static kbd declaration