如何解决使用多个扫描仪

Question

I have aa program that is suppose to take information on the speed of the computer, how much ram the computer has, etc etc(Basically a computer inventory system). Nothing is really wrong with the program as far as I know. The only problem I have is that I do not want to use multiple scanner since I've read it's considered bad practice. The scenario is I have the main method, public static void main, acting as a menu system(The user simply inputs the choice that he wants). Then there are other methods that asks information like how fast is your computer, how much ram does your computer, or even if you would like to remove a computer from your inventory system. Each of these methods have a scanner object and I want to know how I can trim it down to one scanner that could interact with all the data.

Update: Here is a the complete program of the program.

package computerinventory;

import java.util.Scanner;
import java.util.ArrayList;

public class ComputerInventory 
{
private static Scanner read = new Scanner(System.in);

public static void main(String[] args) 
{ 
    ComputerInventory process = new ComputerInventory();
    ArrayList<Computer> computer = new ArrayList<>();

    int option;

    do
    {
        System.out.println("1.) Add computers to your inventory.");
        System.out.println("2.) Display your Inventory.");
        System.out.println("3.) Remove Computers from your inventory.");
        System.out.println("4.) Quit the program. ");
        option = read.nextInt();

        switch(option)
        {
            case 1:
                process.addComputers(computer);
                System.out.println("");
                break;
            case 2:
                process.displayInventory(computer);
                System.out.println("");
                break;
            case 3:
                process.removeComputer(computer);
                break;
            case 4:
                System.out.println("\nThank you for using my program.");
                return;
            default:
                System.out.println("\nThis choice doesn't exist in the menu.");
        }
    }
    while(true);
}

public void addComputers(ArrayList<Computer> computer)
{
    double computerSpeed;
    int hardDrive;
    double ram;
    boolean functional;
    double cost;

    System.out.println("\nHow fast is this computer in Ghz?");
    computerSpeed = read.nextDouble();

    System.out.println("\nHow big is the HardDrive in GB?");
    hardDrive = read.nextInt();

    System.out.println("\nHow much ram does this computer has. ");
    ram = read.nextDouble();

    System.out.println("\nTrue or false, does this computer work?");
    functional = read.nextBoolean();

    System.out.println("\nHow much does this computer cost? ");
    cost = read.nextDouble();

    Computer com = new Computer(computerSpeed, hardDrive, ram, functional, cost);
    computer.add(com);
}

public void displayInventory(ArrayList<Computer> computer)
{   
   for (Computer computer1 : computer) 
   {
       System.out.println(computer1);
   }
}

public double totalCost()
{
    return 0;
}

public void removeComputer(ArrayList<Computer> computer)
{

}
}







package computerinventory;


public class Computer 
{
private double computerSpeed;
private int hardDrive;
private double ram;
private boolean functional;
private double cost;

public Computer(double computerSpeed, int hardDrive, double ram, boolean functional, double cost) 
{
    this.computerSpeed = computerSpeed;
    this.hardDrive = hardDrive;
    this.ram = ram;
    this.functional = functional;
    this.cost = cost;
}

public Computer()
{

}

public void setComputerSpeed(double computerSpeed) 
{
    this.computerSpeed = computerSpeed;
}

public void setHardDrive(int hardDrive) 
{
    this.hardDrive = hardDrive;
}

public void setRam(double ram) 
{
    this.ram = ram;
}

public void setFunctional(boolean functional) 
{
    this.functional = functional;
}

public void setCost(double cost) 
{
    this.cost = cost;
}

@Override
public String toString() 
{
    return "\nSpeed is " + computerSpeed + " GHz.\n" + "hardDrive is " + hardDrive 
     + " GigaBytes.\n" + "RAM is " + ram + "GigaBytes.\n" + "Status is " + functional
     + "\n" + "The cost of this computer " + cost;
}

}

Answer 1

You can use the Scanner method in the main class and possibly prompt for inputs in the main class.

public static void main(String[] args)
{
 // Scanner object created here
 // Ask for information here, variables a and b
 // ArrayList that is suppose to contain all the information.

 // menu here with four choices
}

public void doSomething(ArrayList<ClassName> obj, int a, int b)
{
 // Add paramater variables to the existing array list
}

 // More methods as you go down with a scanner object.

Answer 2

Here I use one scanner to gather all of the data, if you'd like, I can post an update at your request passing the scanner to the method also. This same practice works with pretty much any data type.

You can expand on this to use ArrayLists, which would be pretty easy also.
try this code out:

    public static void main (String [] args) {
    Scanner input = new Scanner (System.in);
    int data1;
    int data2;
    int data3;

    System.out.println ("Enter data1: ");
    data1 = input.nextInt(); //Can use .nextDouble/float/long/short/byte/line/char... ();
    System.out.println ("Enter data2: ");
    data2 = input.nextInt();
    data3 = manipData (data1, data2);

    System.out.println (data1 + " + " + data2 + " = " + data3);

    input.close(); // Be sure to close your scanner
}

public static int manipData (int data1, int data2) {
    return data1 += data2;
}

Answer 3

Declare the Scanner at level class as a static field. In this way, you have a single Scanner instance available to all the methods of this class and available for other classes as well.

public class X {
    public static Scanner scanner;

    public static void main(String[] args) {
        scanner = new Scanner(System.in);
        //...
        foo();
        //...
        scanner.close();
    }

    public static void foo(...) {
        System.out.println("Please enter the value of x:");
        int x = scanner.nextInt();
        System.out.println("The result of working with X: " + realMethod(x));
    }

    public static int realMethod(int x) {
        int result = ...; //some operations done with an X parameter
        return result;
    }
}