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

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.");
		
	}
}