Using user input to create a new object [JAVA]

Question

Hi I am trying to create a program to create a new object whenever the user inputs a new information for a certain object. Currently I have this.

import java.util.Scanner;
public class Main
{
    public static void main (String args[]) 
{
    String input;
    Scanner scanner = new Scanner(System.in);
    do
    {
        System.out.println("Computer Menu");  
        System.out.println("1. Add a new Desktop Information");
        System.out.println("2. Add a new Laptop Information");
        System.out.println("3. Display all Computer Information");
        System.out.println("4. Quit");

        System.out.print("Please enter either 1 to 4: "); 
        input =(scanner.nextLine());
        if (input.equals("1"))
        {
            Desktop desktop1 = new Desktop();
            System.out.println("Please enter Desktop ID: ");
            desktop1.setID (scanner.nextLine());
            System.out.println("Please enter Desktop Processor Speed: ");
            desktop1.setProcess (Double.parseDouble(scanner.nextLine()));
            System.out.println("Please enter Desktop RAM: ");
            desktop1.setRam (Double.parseDouble(scanner.nextLine()));
            System.out.println("Please enter Desktop Harddisk Space: ");
            desktop1.setDisk (Double.parseDouble(scanner.nextLine()));
            System.out.println("Please enter Desktop Monitor Type: ");
            desktop1.setMonitor (scanner.nextLine());
            System.out.println("Please enter Desktop Price: ");
            desktop1.setPrice (Double.parseDouble(scanner.nextLine()));
            desktop1.displayComputer();
        }
        else if (input.equals("2"))
        {
            Laptop laptop1 = new Laptop();
            System.out.println("Please enter Laptop ID: ");
            laptop1.setID (scanner.nextLine());
            System.out.println("Please enter Laptop Processor Speed: ");
            laptop1.setProcess (Double.parseDouble(scanner.nextLine()));
            System.out.println("Please enter Laptop RAM: ");
            laptop1.setRam (Double.parseDouble(scanner.nextLine()));
            System.out.println("Please enter Laptop Harddisk Space: ");
            laptop1.setDisk (Double.parseDouble(scanner.nextLine()));
            System.out.println("Please enter Laptop Weight: ");
            laptop1.setWeight (Double.parseDouble(scanner.nextLine()));
            System.out.println("Please enter Laptop Price: ");
            laptop1.setPrice (Double.parseDouble(scanner.nextLine()));
            laptop1.displayComputer();
         }

Computer super class

public class Computer
{
    String ID;
    double process;
    double ram;
    double disk;
    double price;

    void setID (String _id)
    {
        ID = _id;
    }
    void setProcess (double _Process)
    {
        process = _Process;
    }
    void setRam (double _Ram)
    {
        ram = _Ram;
    }
    void setDisk (double _Disk)
    {
        disk = _Disk;
    }
    void setPrice (double _Price)
    {
        price = _Price;
    }

    String getID()
    {
        return ID;
    }
    double getProcess()
    {
        return process;
    }
    double getRam()
    {
        return ram;
    }
    double getDisk()
    {
        return disk;
    }
    double getPrice()
    {
        return price;
    }

    void displayComputer()
    {
        System.out.println("Computer ID: " + getID());
        System.out.println("Processor Speed: " + getProcess());
        System.out.println("RAM: " + getRam());
        System.out.println("Harddisk: " + getDisk());
        System.out.println("Price: " + getPrice());
    }
}

Desktop sub class

public class Desktop extends Computer
{
    String monitor;

    void setMonitor (String _Monitor)
    {
        monitor = _Monitor;
    }
    String getMonitor()
    {
        return monitor;
    }

    void displayComputer()
    {
        System.out.println("Computer ID: " + getID());
        System.out.println("Processor Speed: " + getProcess());
        System.out.println("RAM: " + getRam());
        System.out.println("Harddisk: " + getDisk());
        System.out.println("Monitor Type: " + getMonitor());
        System.out.println("Price: " + getPrice());
        System.out.println("");
    }
}

Laptop sub class

public class Desktop extends Computer
{
    double Weight;

    void setWeight(String _Weight)
    {
        Weight= _Weight;
    }
    String getWeight()
    {
        return Weight;
    }

    void displayComputer()
    {
        System.out.println("Computer ID: " + getID());
        System.out.println("Processor Speed: " + getProcess());
        System.out.println("RAM: " + getRam());
        System.out.println("Harddisk: " + getDisk());
        System.out.println("Weight: " + getWeight());
        System.out.println("Price: " + getPrice());
        System.out.println("");
    }
}

So There is one class and 2 sub classes but I don't think it matters. So if i entered 1 it should create a new object for Desktop and if i entered 2 it would create a new object for Laptop. And when I enter 3 it should show all the objects created. I don't know how to get any of them to work please help.

Store the object state in HashMap or any other collection i.e. when the input is 1, create the Desktop Object and store in the collection, when the user click on 2, create the Laptop Object and store in the same collection and when the user's input is 3 print or iterate the collection and get the Object information. — Ankush soni
– Ankush soni, Commented Aug 18, 2015 at 12:40

Matt · Accepted Answer · 2015-08-20 15:22:13Z

With the limit information provided by you I try to solve the issue:

I am not adding any attributes to Desktop and Laptop class, overriding toString Method in both the Classes i.e.


public class Laptop {
    public String toString() {
        return "Laptop [getClass()=" + getClass() + ", hashCode()="
                + hashCode() + ", toString()=" + super.toString() + "]";
    }
}


public class Desktop {
    public String toString() {
        return "Desktop [getClass()=" + getClass() + ", hashCode()="
                + hashCode() + ", toString()=" + super.toString() + "]";
    }
}

Your Main method look like:

public static void main (String args[]) 
    {
        String input;
        Scanner scanner = new Scanner(System.in);
        List<Object> listOfObject = new ArrayList<>();
        do
        {
            System.out.println("Computer Menu");  
            System.out.println("1. Add a new Desktop Information");
            System.out.println("2. Add a new Laptop Information");
            System.out.println("3. Display all Computer Information");
            System.out.println("4. Quit");

            System.out.print("Please enter either 1 to 4: "); 
            input =(scanner.nextLine());
            if (input.equals("1")){
                Desktop desktop1 = new Desktop();
                listOfObject.add(desktop1);
            }else if (input.equals("2")){
                Laptop laptop1 = new Laptop();
                listOfObject.add(laptop1);
             }else if(input.equals("3")){
                 for(Object obj : listOfObject){
                     if(obj instanceof Desktop){
                        Desktop d1 = (Desktop)obj;
                        System.out.println(d1.toString());
                     }else if(obj instanceof Laptop){
                         Laptop l1 = (Laptop)obj;
                         System.out.println(l1.toString());
                     }
                 }
             }
        }while(!input.equals("4"));
    }

Adam · Accepted Answer · 2015-08-18 12:38:29Z

0

Assuming you have a class/interface named Computer from which Laptop and Desktop extend.

1) Add a list to store Computer instances.

List<Computer> computers = new ArrayList<Computer>()

2) Make actions "1" and "2" add to that list, e.g.

computers.add(desktop1);

3) Make action "3" print out the list. This assumes you've implemented toString()

for (Computer computer : computers) {
   System.out.println(computer);
}

answered Aug 18, 2015 at 12:38

Adam

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