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Thread: Alright guys, I am having some serious trouble with this one.

  1. #1
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    Default Alright guys, I am having some serious trouble with this one.

    Here is one part of the project that is stumping me. I don't think I understand how this stuff works. Here is what I have to try to accomplish...

    "write a program that uses the purchase class to set the following prices:

    oranges, 10 for 2.99
    eggs, 12 for 1.69
    apples, 3 for 1.00
    watermelons, 4.39 each
    bagels, 6 for 3.50

    Then calculate the total bill for each item for the following:

    2 dozen oranges
    3 dozen eggs
    20 apples
    2 watermelons
    1 dozen bagels"

    here is the purchase class that is referenced in the question...

    import java.util.Scanner;
    /**
    Class for the purchase of one kind of item, such as 3 oranges.
    Prices are set supermarket style, such as 5 for $1.25.
    */
    public class Purchase
    {
    	private String name;
    	private int groupCount; //Part of a price, like the 2 in 2 for $1.99.
    	private double groupPrice; //Part of a price, like the $1.99.
    	//in 2 for $1.99.
    	private int numberBought; //Number of items bought.
     
    	public void setName (String newName)
    	{
    		name = newName;
    	}
     
    	/**
    	Sets price to count pieces for $costForCount.
    	For example, 2 for $1.99.
    	*/
    	public void setPrice (int count, double costForCount)
    	{
    		if ((count <=0) || (costForCount <=0))
    		{
    			System.out.println ("Error: Bad parameter in setPrice.");
    			System.exit (0);
    		}
    		else
    		{
    			groupCount = count;
    			groupPrice = costForCount;
    		}
    	}
     
    	public void setNumberBought (int number)
    	{
    		if (number <= 0)
    		{
    			System.out.println ("Error: Bad parameter in setNumberBought.");
    			System.exit (0);
    		}
    		else
    		{
    			numberBought = number;
    		}
    	}
     
    		/**
    		Reads from the keyboard the price and number of a purchase.
    		*/
    		public void readInput ()
    		{
    			Scanner keyboard = new Scanner (System.in);
    			System.out.println ("Enter name of item you are purchasing:");
    			name = keyboard.nextLine ();
    			System.out.println ("Enter the price of an item as 2 numbers.");
    			System.out.println ("For example, 3 for $2.99 is entered as");
    			System.out.println ("3 2.99");
    			System.out.println ("Enter the price of an item as two numbers, now:");
    			groupCount = keyboard.nextInt ();
    			groupPrice = keyboard.nextDouble ();
    			while ((groupCount <= 0) || (groupPrice <= 0))
    			{ //Try again:
    				System.out.println ("Both numbers must be positive.  Try again.");
    				System.out.println ("Enter the price of an item as 2 numbers.");
    				System.out.println ("For example, 3 for $2.99 is entered as");
    				System.out.println ("3 2.99");
    				System.out.println ("Enter the price of an item as two numbers, now:");
    				groupCount = keyboard.nextInt ();
    				groupPrice = keyboard.nextDouble ();
    			}
    			System.out.println ("Enter the number of items purchased:");
    			numberBought = keyboard.nextInt ();
    			while (numberBought <= 0)
    			{ //Try again:
    				System.out.println ("The number must be positive.  Try again.");
    				System.out.println ("Enter the number of items purchased:");
    				numberBought = keyboard.nextInt ();
    			}
    		}
     
    		/**
    		Displays the price and number being purchased
    		*/
    		public void writeOutput ()
    		{
    			System.out.println (numberBought + " " + name);
    			System.out.println ("at " + groupCount + " for $" + groupPrice);
    		}
    		public String getName ()
    		{
    			return name;
    		}
     
    		public double getTotalCost ()
    		{
    			return (groupPrice / groupCount) * numberBought;
    		}
     
    		public double getUnitCost ()
    		{
    			return groupPrice / groupCount;
    		}
     
    		public int getNumberBought ()
    		{
    			return numberBought;
    		}
    }

    Can someone give me some insight as to what I am supposed to be doing. I don't think I understand the question.


  2. #2
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    Default Re: Alright guys, I am having some serious trouble with this one.

    Your doing to much in one class. Try separating into a different class (or several, if you'd like) that you can instantiate as just a data class. Then move all your input/output to a seperate class (MainDriver is a good name, Driver if you are sure you won't have to input any of the packages that have a class named that, such as java.sql.Driver), that way you can has-a with Product.

    An example would be
    class Product has methods getName, setName, getUnitCost, getGroupCost, getGroupSize, setUnitCost, setGroupCost, setGroupSize, getNumBought, and buy. (buy would add one to number bought)

    class MainDriver has main and any helper methods necessary.

    A google search found a decent tutorial on data classes in java.
    Java Object Oriented Programming User-Defined Classes

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