How to use void methods

Question

I need to display the following information

Enter size of array: 3
Enter student name: jane doe
Enter student id number: 14234567
Enter student name: john doe
Enter student id number: 12345678
Enter student name: peter griffin
Enter student id number: 14238251
Array Contents
jane doe 14234567
john doe 12345678
peter griffin
14238251

i have to use the following methods

To ask the user for the size they wish the array to be and then create an array of type Student of the specified size.

public static Student[] createArray()

To populate the array by asking the user to input a name and ID number for each object stored within the array

public static void populateArray(Student[] array)

To displays the contents of the array

public static void displayArray(Student[] array)

This is what I have so far

class Student {

    //private instances
    private String name = "unassigned";
    private long idNumber = 0;

    //Default constructor
    public Student() {
    name = "Not Given";
    idNumber = 0;
    }

    //Constructs a new Student with passed name and age parameters.
    public Student(String studentName, long studentIdNumber) {
    name = studentName;
    idNumber = studentIdNumber;
    }

    //Returns the name of this student.
    public String getName( ) {
        return name;
    }

    // Returns the idNumber of this person.
    public long getIdNumber( ) {
        return idNumber;
    }       

    //Sets the name of this student.
    public void setName(String studentName ) {
        name = studentName;
    }

    //Sets the idNumber of this student.
    public void setIdNumber(long studentIdNumber ) {
        idNumber = studentIdNumber;
    }


} // end class

and

import java.util.Scanner;

public class StudentTest {

    static int array;

    //create method createArray
    public static Student[] createArray() {

        Scanner int_input = new Scanner(System.in);

        //user enters size of array         
        System.out.print("Enter Size of Array: ");
        array = int_input.nextInt();

        //create array
        Student[] array = new Student[0];                   
        return array;//return array

    }//end method   

    //create method populateArray
    public static void populateArray(Student[] array) {

        try (Scanner string_input = new Scanner(System.in);
             Scanner long_input = new Scanner(System.in);)
        {               
            for (int i = 0; i < 3; i++) {
                Student arrays = new Student();

                //set name
                System.out.println("Enter Student Name: ");
                arrays.setName(string_input.nextLine());

                //set ID number
                System.out.println("Enter Student ID Number: ");
                arrays.setIdNumber(long_input.nextLong());

                System.out.println();

            }//end for loop
        }//end try loop                             
    }//end method

    //create method display Array
    public static void displayArray(Student[] array){

        System.out.println("Array Contents");
        System.out.println();

    }//end method

    public static void main(String [] args){

        //display createArray method
        System.out.println(createArray());

        //display populateArray method
        System.out.println();

        //display array contents
        System.out.println();

    }//end main method
}//end class

my question is how do i get the populateArray method to allow me to enter data into it and then display it? and get the displayArray method to display? I have tried a number of different things but i can't figure it out

Answer 1

You have to fix a few things according to your logic. Start with main:

public static void main(String [] args) {
    // create array of size specified by user
    Student[] students = createArray();

    // populate this array with data from user
    populateArray(students);

    // finally, display array contents
    displayArray(students);

}//end main method

In createArray create and return array of correct size:

// read user input as arraySize
return new Student[arraySize];

In populateArray make sure you modify passed array with data from user, i.e. :

for (int i = 0; i < 3; i++) {
    Student student = new Student(); // new student

    //set name
    System.out.println("Enter Student Name: ");
    student.setName(scanner.nextLine());

    //set ID number
    System.out.println("Enter Student ID Number: ");
    student.setIdNumber(scanner.nextLong());

    inputArray[i] = student; // put new student into array passed to the method

}//end for loop

And finally, in displayArray just iterate over items and print them in format you like:

public static void displayArray(Student[] students){

    for (Student s : students) {
        System.out.println(String.format("Name = %s, id = %d", s.getName(), s.getIdNumber());
    }
}//end method

And, of course, you don't really need to have 3 different methods to implement this trivial functionality, but it should work.