Problem

Write a program create a simple grocery list. Prompt the user for the number of items in the list. Then prompt the user to enter each item and the amount of each item needed. Use parallel arrays to store the item names and quantities. Finally, print the list of items and a count of the total number of items

Example Output

Grocery List
------------
1 bacon
12 eggs
4 apples

17 items

More with Arrays

Solution

First, prompt the user for the number of items:

String input;        //temp variable for dialog input	
int    listSize = 0; //the number of items for the grocery list, default 0

input = JOptionPane.showInputDialog("Input length:");
listSize = Integer.parseInt(input);

Now that we have the number of items, listSize, we need to get the items and quantities.

//Create arrays for list items and quantity
String[] groceryList     = new String[listSize];
int[]    groceryQuantity = new int[listSize];

//prompt for input listSize times
for( int i = 0; i < groceryList.length; i++ )
{
	//get the name of the item and 
	groceryList[ i ] = JOptionPane.showInputDialog("Item name");

	input = JOptionPane.showInputDialog("How many " + groceryList[ i ] + "?" );
	groceryQuantity[ i ] = Integer.parseInt( input );
	
}

Last step is to print the list out. We will use the loop for printing to sum the quantities.

int itemCount = 0; //sum of the quantities of the items

//Print a header for the list
System.out.println( "Grocery List" );
System.out.println( "------------" );

//loop through and print out the list items
for( int i = 0; i < groceryList.length; i++ )
{
	System.out.println( groceryQuantity[ i ] + " " + groceryList[ i ] );
	itemCount = itemCount + groceryQuantity[ i ];
}

System.out.println( "\n" + itemCount + " items.");

All together we have:

import javax.swing.JOptionPane;

public class grocery {
	public static void main( String[] args )
	{

		String input;        //temp variable for dialog input	
		int    listSize = 0; //the number of items for the grocery list, default 0
		
		input = JOptionPane.showInputDialog("Input length:");
		listSize = Integer.parseInt(input);
		
			
		//Create arrays for list items and quantity
		String[] groceryList     = new String[listSize];
		int[]    groceryQuantity = new int[listSize];
		
		//prompt for input listSize times
		for( int i = 0; i < groceryList.length; i++ )
		{
			//get the name of the item and 
			groceryList[ i ] = JOptionPane.showInputDialog("Item name");
		
			input = JOptionPane.showInputDialog("How many " + groceryList[ i ] + "?" );
			groceryQuantity[ i ] = Integer.parseInt( input );
			
		}
		
		int itemCount = 0; //sum of the quantities of the items
		
		//Print a header for the list
		System.out.println( "Grocery List" );
		System.out.println( "------------" );
		
		//loop through and print out the list items
		for( int i = 0; i < groceryList.length; i++ )
		{
			System.out.println( groceryQuantity[ i ] + " " + groceryList[ i ] );
			itemCount = itemCount + groceryQuantity[ i ];
		}
		
		System.out.println( "\n" + itemCount + " items.");
		
	}
}

Once I have a working example I like to go a step further and simplify the code

1. The loop for prompting the user and the loop for printing the list can be combined.
2. By passing the String returned by JOptionPane to Integer.parseInt you can remove the input variable.

Code

Solution Code

import javax.swing.JOptionPane;

public class grocery2 {
	public static void main( String[] args )
	{

		int  listSize  = 0; //the number of items for the grocery list, default 0
		int  itemCount = 0; //sum of the quantities of the items
		
		listSize = Integer.parseInt( JOptionPane.showInputDialog("Input length:") );

		//Create arrays for list items and quantity
		String[] groceryList     = new String[listSize];
		int[]    groceryQuantity = new int[listSize];
		
		
		//Print a header for the list
		System.out.println( "Grocery List\n------------" );
		
		for( int i = 0; i < listSize; i++ )
		{
			//get the name of the item and 
			groceryList[ i ]     = JOptionPane.showInputDialog("Item name");
			groceryQuantity[ i ] = Integer.parseInt( JOptionPane.showInputDialog("How many " + groceryList[ i ] + "?" ) );
			
			//print the item on quantity to console
			System.out.println( groceryQuantity[ i ] + " " + groceryList[ i ] );
			
			//add the most recent quantity to the item count
			itemCount = itemCount + groceryQuantity[ i ];
		}
		
		System.out.println( "\n" + itemCount + " items.");
		
	}
}