Thread: Help with assignment

Originally Posted by NPVinny

public class BikeShop { 
 
  private Bike[] bikes;
  private int totalbikes;
  private double gross;
  private final static int SIZE = 30;
 
  	//Constructor method
  	public BikeShop() {
  		bikes = new Bike[SIZE];
  		totalbikes = 0;
  		gross = 0.0;
  	}//end constructor method
 
  	//addNew - adds a new bike object to the bike shop
  	public void addNew(Bike b) {
  		if (totalbikes < bikes.length) {
  			bikes[totalbikes] = b;
  			totalbikes++;
  		}//end if
  		else {
  			Bike[] temp = new Bike[totalbikes];
  			int i;
  			int newlength = 2*bikes.length;
  			for (i=0; i<totalbikes;i++)
  				temp[i] = bikes[i];
  			bikes = new Bike[newlength];
  			for (i=0; i<totalbikes; i++)
  				bikes[i] = temp[i];
  			bikes[totalbikes] = b;
  			totalbikes++;
  		}//end else
  	}//end addNew method
 
  	//addQuantity - adds to the quantity of a bike in stock
  	public void addQuantity(String name, int quantity) {
  		int i;
  		for (i=0; i<totalbikes; i++) {
  			if ((bikes[i].getName()).equals(name)) {
  				bikes[i].addStock(quantity);
  				return;
  			}//end if
  		}//end for
  	}//end addQuantity method
 
  	//inStock - checks to see if a given bike in specified quantity is in stock
  	public boolean inStock(String name, int quantity) {
  		int i;
  		for (i=0; i<totalbikes; i++) {
  			if ((bikes[i].getName()).equals(name)) {
  				if (quantity <= bikes[i].getQuantity())
  					return true;
  				else
  					return false;
  			}//end if
  		}//end for
  		return false;
  	}//end inStock method
 
  	//sell - sells a given bike in specified quantity
  	public boolean sell(String name, int quantity) {
  		boolean retval = inStock(name, quantity);
  		if (retval) {
  			int i;
  			for (i =0; i<totalbikes; i++)
  				if (name.equals(bikes[i].getName())) {
  					gross += bikes[i].sell(quantity);
  					if (bikes[i].getQuantity() == 0) {
  						delete(i);
  					}//end if
  					break;
  				}//end if
          }//end for
  		return retval;
  	}//end sell method
 
  	//listNames - lists the names of all bikes in stock and the quantity on hand
  	public void listNames() {
  		int i;
  		System.out.println();
  		System.out.println("Name                                   Quantity");
  		for (i=0;i<totalbikes;i++) {
  			System.out.print((i+1)+". "+bikes[i].getName());
  			int spaceused = (int)(Math.floor(Math.log(i+1)/Math.log(10)))+1;
  			spaceused += (bikes[i].getName()).length() + 2;
  			int spaces = 40 - spaceused;
  			if (spaces <= 0) spaces = 1;
  			for (int j=0;j<spaces;j++)
  				System.out.print(" ");
  			System.out.println(bikes[i].getQuantity());
  		}//end for
  		System.out.println();
  	}//end listNames method
 
  	//listDetails - prints all information about in stock bikes
  	public void listDetails() {
  		int i;
  		System.out.println();
  		System.out.println("Name                    Size        Color            Price          Quantity");
  		for (i=0;i<totalbikes;i++) {
  			System.out.print((i+1)+". "+bikes[i].getName());
  			int spaceused = (int)(Math.floor(Math.log(i+1)/Math.log(10)))+1;
  			spaceused += (bikes[i].getName()).length() + 2;
  			int spaces = 25 - spaceused;
  			if (spaces <= 0) spaces = 1;
  			for (int j=0;j<spaces;j++)
  				System.out.print(" ");
  			System.out.print(bikes[i].getSize());
  			System.out.print("           ");
  			System.out.print(bikes[i].getColor());
  			spaceused = (int)(Math.floor(Math.log(i+1)/Math.log(10)))+1;
  			spaceused += (bikes[i].getColor()).length() + 2;
  			spaces = 18 - spaceused;
  			if (spaces <= 0) spaces = 1;
  			for (int j=0;j<spaces;j++)
  				System.out.print(" ");
  			System.out.print(bikes[i].getPrice());
  			System.out.print("             ");
  			System.out.println(bikes[i].getQuantity());
  		}//end for
  		System.out.println();
  	}//end listDetails method
 
  	//getIncome - return how much $ the shop has made
  	public double getIncome() {
  		return gross;
  	}

public class Bike
 
{
 
	private String name;
	private int size;
	private String color;
	private double price;
	private int quantity;
 
	public Bike(String theName, int itsSize, String itsColor, double cost, int qty) {
	}
 
 
	public String getName() {
		return name;
	}
 
	public int getSize() {
		return size;
	}
 
	public String getColor() {
		return color;
	}
 
	public double getPrice() {
		return price;
	}
 
	public int getQuantity() {
		return quantity;
	}
 
	public String toString() {
		//Not used in program
	}
 
	public void reduceStock(int change) {
		if (quantity > 0 && change <= quantity) 
			quantity -= change;
		return;
 
	}
 
	public void addStock (int change) {
		quantity += change;
		return;
	}
 
	public double sell(int num) {
 
		if (quantity > 0 && num <= quantity) {
			reduceStock(num);
		}
			else
				System.out.println("Sorry, but there are not enough bikes to sell.");
		return num*price;
	}
 
 
 
}

import java.util.*;
 
public class MyBikeShop {
 
	public static int menucode;
	public static BikeShop VinnyBikeShop = new BikeShop();
	public static Bike aBike;
	public static String name;
	public static int size;
	public static String color;
	public static int quantity;
	public static int num;
	public static double price;
 
 
	public static void main(String[] args) {
 
	Scanner input = new Scanner(System.in);
	String lineSeparator = System.getProperty("line.separator");
	input.useDelimiter(lineSeparator);
 
	while (menucode != 6) {
	System.out.println("====================================================================");
	System.out.println("                         Vinny's Bike Shop");
	System.out.println("====================================================================");   
    System.out.println("1 - Add a bike to the stock");
	System.out.println("2 - Sell a bike in stock");
	System.out.println("3 - List the names and sizes of the bikes in stock");
	System.out.println("4 - List all information about the bikes in stock");
	System.out.println("5 - Print out the total amount of sales of the bike shop");
	System.out.println("6 - Quit");
	System.out.print("\nPlease Select an Option: \n");
 
	menucode = input.nextInt();
 
 
	if (menucode == 1) {
 
 
		System.out.print("Please enter the name of the bike to be added:\n");
		name = input.next();
 
		if (VinnyBikeShop.inStock(name, 0)) {
	        System.out.print("The bike is NOT in stock. It will need to be added.\n");
			System.out.println("What is the size of the bike?");
			size = input.nextInt();
			System.out.println("What is the color of the bike?");
			color = input.next();
			System.out.println("How many bikes do you want to add?");
			quantity = input.nextInt();
			System.out.println("What is the price of the bike?");
			price = input.nextDouble();
			aBike = new Bike(name, size, color, price, quantity);
			VinnyBikeShop.addNew(aBike);
	        }
 
                        if (VinnyBikeShop.inStock(name, quantity)) { 
			System.out.println("That bike is in stock");
			System.out.println("How many would you like to sell?");
                       }
 
	}
 
	else if (menucode == 2) 
		//Menu choice for selling a bike.
 
	else if (menucode == 3) 
		VinnyBikeShop.listNames();
 
	else if (menucode == 4) 
		VinnyBikeShop.listDetails();
 
	else if (menucode == 5) 
		VinnyBikeShop.getIncome();
 
	}	
 
	System.exit(0);
 
	}
 
}

Here might be one source of error:

Scanner input = new Scanner(System.in);

Maybe I'm wrong, but normally every time I've done that Scanner thing, I've done made it static.
Also, I normally put that Scanner declaration before the main method.

Also, I think input has to be static because the main method is static. However, I do think you went overboard with the statics.

Also, I don't think the compiler likes it if you user a non-static variable from a static context or maybe it was the a static variable from a non-static context.

In any case, since the Bikes array bikes is of length SIZE, why not put that instead of bikes.length to shorten the code a little bit?

Also, until you initialize the values you're passing as parameters, your constructor won't like them and will likely throw some error there saying that each of the parameters might not have been initialized and your get methods will likely return null, if not throw a NullPointerException.

Also, in case your wondering about Exceptions, here's a common one

try
{ // try block looks for exception and goes to catch if it throws it.  Your own exception classes must be thrown in the try block with the words throw and new yourExceptionClass
 
int i;
 
i = input.nextInt();
}
 
catch)InputMismatchException imeRef)
{ // catch handles exception.  In this case, this one handles it if you have the wrong input type, i.e., entering 3.14 or Bob for an integer value
 
System.out.println("Exception " 
                             + imeRef.toString());
} 
catch (ArithmeticException aeRef)
{ // this one handles if you do something like divide by zero
 System.out.println("Exception" + aeRef.toString());
}

You probably don't need to worry about exceptions yet, but just something to think about.



And what does += mean?

spaceused += (bikes[i].getName()).length() + 2;

Also, doesn't menuCode have to be initialized to some value?

In fact, don't all of your variables have to be initialized?

	//addNew - adds a new bike object to the bike shop
  	public void addNew(Bike b) {
  		if (totalbikes < bikes.length) {
  			bikes[totalbikes] = b;
  			totalbikes++;
  		}//end if

Couldn't you make a new bike object by doing this:

Bike b = new Bilke(Bike parameters);(

However, you have totalbikes = 0 in constructor and never changed that before if...else loop begins so else part should never happen as it is now. However, if you want totalbikes to be the number of bikes you have, a.k.a., quantity, then why not do this:

Bike b = new Bike(Bike Parameters);
totalbikes = b.getQuantity();

Also, it, though it could be because I'm very tired right now, almost looks like you're telling it to set it to the Bike array to totalbikes. However, as you can keep adding, you're array should get larger. But once array Bike[] temp can't keep being enlarged, at least that's what I heard, that you can't just make an existing array larger, you have to make a whole new array. That's why they invented vectors.

For vectors, it's

Vector<Integer>  vectorNameOne= new Vector<Integer>;
Vector <String> vectorNameTwo = new Vector<String>;
Vector <Double> vectorNameThree = new Vector<Double>;
Vector<Long> vectorNameFour = new Vector<Long>;
Vector<Float> vectorNameFive = new Vector<Float>;
Vector<Boolean> vectorNameSix = new Vector<Boolean>; // why anyone would have a vector of booleans I don't know, but there could be cases where they might have to I guess.
Vector<Char> vectorNameSeven = new Vector<Char>;
Vector <Short> vectorNameEight = new Vector<Short>;
Vector<someClass> vectorNameNine= new Vector<someClass>;
Vector<Bike> bikeVector = new Vector<Bike>;

http://java.sun.com/j2se/1.3/docs/api/java/util/Vector.html#copyInto%28java.lang.Object[]%29

I'm getting rather tired right now.
I'll come back tomorrow.

please use [code] tags, or even better, [highlight="Java"] tags

// why anyone would have a vector of booleans I don't know, but there could be cases where they might have to I guess.

A 1-D vector of booleans is extremely useful for implementing the sieve of eratosthenes (finding prime numbers), though personally I would either use a boolean array or an ArrayList of booleans, even if I decided to use multi-threaded approach to implementing the sieve (I rarely use vectors in Java).

There is also nothing wrong with declaring a Scanner object inside a method (I usually do this).

What I suspect is the problem is that your bike constructor does not actually set anything.

public Bike(String theName, int itsSize, String itsColor, double cost, int qty) {
    // need to actually set the object variables in here
    this.name = theName;
    this.size = itsSize;
    this.color = itsColor;
    this.price = cost;
    this.quantity = qty;
}

Ok, maybe nothing wrong with having it inside the main method I suppose. However, main is static. Shouldn't Scanner be static too?

Also, when I was suggesting Vectors, it was because he had something like:

if (totalbikes < bike.length)
{
something
}
 
else
{
Bike[] temp = new  Bike[totalbikes];
}

or something like that.

I heard that you can't just increase the size of the array.

It's preference really in that case. There's nothing wrong with declaring it inside the main method because then it will be local to the main method.

It's true you can't just "increase" the size of an existing array. You must allocate a new bigger array, then copy over all the old data. Indeed, this is what the underlying implementations of Vector and ArrayList do (of course, they increase the capacity by more than 1 so you don't need to keep re-allocating and copying every time a new item is added to them).

// A sample of how a simple Vector class could be implemented
public class MyVector<Type>
{
     private Type[] data;
     private int length;
 
    public MyVector()
    {
        // initial capacity: 10
        data = new Type[10];
        length = 0;
    }
 
    public Type get(int index)
    {
        if (index < 0 || index >= length)
        {
            throw new ArrayIndexOutOfBoundsException(index);
        }
        return data[index];
    }
 
    public void add(Type item)
    {
        if(length >= Capacity)
        {
            // need to increase the array size
            Type[] temp = new Type[data.length * 2];
            // copy over old data
            for(int i = 0; i < data.length; i++)
            {
                temp[i] = data[i];
            }
            data = temp;
        }
        data[length] = item;
        length++;
    }
 
    public int size()
    {
        return length;
    }
 
    public Type remove(int index)
    {
        Type item = get(index);
        for(int i = index+1; i < length; i++)
        {
            data[i-1] = data[i];
        }
        length--;
        return type;
    }
}