Sorting Arrays

I am having much difficulty getting this program to sort the DVD titles. Could someone please point me in the right direction or show me where or what I am doing wrong. The code will not compile due to errors related to the sorting code. I have read a bunch of information and am not sure where to go from here.

// DVDProducts.java
import java.util.List; // list products
import java.util.ArrayList; // basic array operations
import java.text.DecimalFormat; // formatting decimal
import java.util.Collections; // sorting arrays
 
 
 public class DVDProducts
 {
public static void main(String args[])
{
List <DVD> List = new ArrayList <DVD> ();

// For adding product information
List.add(new DVD(1, "Anna and the King",5,  14.99  ));
List.add(new DVD(2, "A Beautiful Mind ",8,   7.99  )); 
List.add(new DVD(3, "Collateral       ",25,  19.99  ));
List.add(new DVD(4, "Man on Fire      ",12,   9.99  ));
List.add(new DVD(5, "Upside of Anger  ",2,    6.99  ));
List.add(new DVD(6, "Somethings Gotta Give",14,5.99  ));
List.add(new DVD(7, "Matrix           ",20,   9.99  ));
List.add(new DVD(8, "No Country for Old Men",30,29.99  ));
List.add(new DVD(9, "Gladiator        ",9,   13.99  ));
List.add(new DVD(10, "Jaws            ",3,    4.95  ));
List.add(new DVD(11, "Heist           ",18,  14.95  ));
List.add(new DVD(12, "Lucky Number Slevin",9,7.95  ));
List.add(new DVD(13, "Shooter         ",11,  10.95  ));
List.add(new DVD(14, "Badder Santa    ",3,    4.99  ));
List.add(new DVD(15, "The Departed    ",15,   9.99  ));
List.add(new DVD(16, "Wall Street     ",6,    3.99  ));
List.add(new DVD(17, "Million Dollar Baby",13,12.99  ));
List.add(new DVD(18, "The Usual Suspects",10,12.95  ));
List.add(new DVD(19, "V for Vendetta  ",22,   9.95  ));
List.add(new DVD(20, "True Crime      ",2,    6.99  ));

//Display Inventory
System.out.println("");
System.out.println("Item Number\tDVD Title\tStock Units\tUnit Price\tUnit Value");
System.out.println("--------------------------------------------------------------------------------");
DecimalFormat df = new DecimalFormat("$#.00");

for (int i = 0; i < List.size; i++)
{
System.out.println("list "+ i +" : " +(String) List.get(i));
} // end for

Collections.sort(List);

for (int i = 0; i < List.size; i++)
{
System.out.println("list " + i + " : " + (String) List.get(i));
}// end for

for (int i= 0; i < List.size(); i++)
{
int size = List.size(i);
DVD dvd = List.get(i);
  System.out.println(dvd.getProdNumber()+"\t "+dvd.getdvdTitle()+"\t   "+dvd.getStockUnit()+"\t         "+df.format(dvd.getUnitPrice())+"\t           "+df.format(dvd.unitValue()));
}// end for

} // end main method
 
} // end class DVDProducts

// DVD.java
 
class DVD 
 {
private int prodNumber; // product number
private String dvdTitle; // DVD Title
private int stockUnit; // in stock units
private Double unitPrice; // unit price
 
{
 
}
 
public DVD () {}// default constructor
public DVD(int prodNumber, String dvdTitle, int stockUnit, double unitPrice)
{
//Constructor
this.prodNumber = prodNumber;
this.dvdTitle = dvdTitle; 
this.stockUnit = stockUnit; 
this.unitPrice = unitPrice;
}
 
// Set and Get method
public void setProdNumber(int prodNumber)
{
this.prodNumber = prodNumber;
} // end set product number
 
public int getProdNumber()
{
return prodNumber;
} // end get product number
 
public void setDVDTitle(String DVDTitle)
{
this.dvdTitle = dvdTitle;
} // end set DVD Title
 
public String getdvdTitle()
{
return dvdTitle;
} // end get DVD Title

public void setStockUnit(int stockUnit)
{
this.stockUnit = stockUnit;
} // end set in stock unit
 
public int getStockUnit()
{
return stockUnit;
} // end get in stock unit
 
public void setUnitPrice(double unitPrice)
{
this.unitPrice = unitPrice;
} // end set unit price
 
public double getUnitPrice()
{
return unitPrice;
} // end get unit price

public double unitValue()
{
return stockUnit * unitPrice;
} // end get total value
 
} // end class DVD

Chris,

I see five errors that are simple syntax issues. You should follow what the compiler tells you the errors are.

As for the error on Collections.sort(List);, the API for Collections.sort(List<T>) explains what is required of the elements of the list in order for the list to be sorted via this method. DVD doesn't meet these requirements.
[ May 09, 2008: Message edited by: Stevi Deter ]

I have reworked this program several times with different sorting methods. I cannot get this thing to compile nor can I see where the problem is.

Would someone please tell me what the problem is with this program?

// Product.java
 
class Product 
{
private int itemNumber;// item number
private String title;// item title
private int units;// number of units int stock
private double price;// price of each unit

public Product(int itemNumber, String title, int units, double price) 
{
// Constructor 
this.itemNumber = itemNumber;
this.title = title;
this.units = units;
this.price = price;
}

// Get and set methods
public void setItemNumber(int itemNumber) 
{
this.itemNumber = itemNumber;
}// end setItemNumber
public int getItemNumber() 
{
return itemNumber;
}// end setItemNumber
public void setTitle(String title) 
{
this.title = title;
}// end setTitle
public String getTitle() 
{
return title;
}//end getTitle

public void setUnits(int units) 
{
this.units = units;
}//end setUnits
public int getUnits() 
{
return units;
}//end getUnits
public void setPrice(double price) 
{
this.price = price;
}//end setPrice
public double getPrice() 
{
return price;
}// end getPrice

public double calculateInventory() 
{
return units * price;

}// end computeInventory
}//end class Product

// DVDProducts.java
import java.util.ArrayList; // sort arays
import java.util.List; // for adding products
import java.text.DecimalFormat; // decimal formating 
 
public class DVDProducts
 {
 public static Product[] bubbleSort(Product[] products)
 {
 //Sort product by title
 for (int i=0; i<products.length; i++)
 {
 for(int j=i+1; j<products.length; j++)
 {
 String title1 = products[i].gettitle();
 String title2 = products[j].gettitle();
 if (title1.compareTo(title2)>0)
 {
 Product temp = products[i];
 products[i] = products[j];
 products[j] = temp;
 } // end if
 } // end for
 } // end for
 return products;
 } // end Product
 
 public static double calculateAll(Product[] products)
 {
 // calculate total inventory
 double value = 0.0;
 for (int i=0; i<products.length; i++)
 {
 value = value + products[i].calculateInventory();
 
 }// end for
 return value;
 } // end calculate all
 
 
 public static void main(String args[])
{
Product products[] = new Product[20];

// For adding product information
products[0] = new Product(  1, "Anna and the King1  ", 5,  14.99  );
products[1] = new Product(  2, "A Beautiful Mind2   ", 8,   7.99  ); 
products[2] = new Product(  3, "Collateral3         ",25,  19.99  );
products[3] = new Product(  4, "Man on Fire4        ",12,   9.99  );
products[4] = new Product(  5, "Upside of Anger5    ", 2,   6.99  );
products[5] = new Product(  6, "Somethings Gotta Give6 ",14,5.99 );
products[6] = new Product(  7, "Matrix7             ",20,   9.99  );
products[7] = new Product(  8, "No Country for Old Men8 ",30,29.99  );
products[8] = new Product(  9, "Gladiator9          ", 9,  13.99  );
products[9] = new Product( 10, "Jaws10              ", 3,   4.95  );
products[10] = new Product(11, "Heist11             ",18,  14.95  );
products[11] = new Product(12, "Lucky Number Slevin12  ",9,7.95  );
products[12] = new Product(13, "Shooter13           ",11,  10.95  );
products[13] = new Product(14, "Badder Santa14      ", 3,   4.99  );
products[14] = new Product(15, "The Departed15      ",15,   9.99  );
products[15] = new Product(16, "Wall Street16       ", 6,   3.99  );
products[16] = new Product(17, "Million Dollar Baby17  ",13,12.99  );
products[17] = new Product(18, "The Usual Suspects18",10,12.95  );
products[18] = new Product(19, "V for Vendetta19    ",22,   9.95  );
products[19] = new Product(20, "True Crime20        ", 2,   6.99  );

// Sort by title
products = bubbleSort(products);

//Display Inventory
System.out.println("");
System.out.println("Item Number\tTitle\tUnits\tUnit Price\tInventory Value");
System.out.println("--------------------------------------------------------------------------------");
 DecimalFormat df = new DecimalFormat("$#.00");
 for (int i = 0; i < products.length; i++);
 {
 Product product = products[i];
 System.out.println(product.getItemNumber()+"\t"+product.getTitle()+"\t"+df.format(product.getUnits())+"\t"+df.format(product.getPrice())+"\t"+df.format(product.calculateInventory()));
} // end for
System.out.println("\nTotal value of the inventory: " + df.format(calculateAll(products)));
}// end main
}// end class Products

Originally posted by Stevi Deter:
You should follow what the compiler tells you the errors are.

Start at the first compiler error and work from there.

The compiler tells me that it cannot find the symbols for line 15 and 16 or class DVDProducts which is:
String title1 = products[i].gettitle();
String title2 = products[j].gettitle();

I don't have a clue as to where else there should be a symbol in the code. I have checked this against a number of examples and I am baffled.

Are you sure that the gettitle method exists? Hint: Java is case sensitive.

Are you using any IDE like eclipse or just using a text pad?

After you finish getting all the bugs out and compiling your program, here is some more advice:

I see you used encapsulization (making your class variables private and get and set methods public) but in the case of your program I think you are using encapsulizing several times where you do not need to. For example, you have this code:

public void setTitle(String title) {
this.title = title;
}// end setTitle
public String getTitle() {
return title;
}//end getTitle

Ask yourself, what is the difference between these two statements?
myProduct.title = "Killer Martians";
myProduct.setTitle("Killer Martians");

When I encapsulize, I do it in order to protect my class variables from being set to something I don't want them to be set to, for example:

class DividingTime{
private int divideByThisInt = 1;

public void setTheInt(int newInt){
if (newInt != 0){
divideByThisInt = newInt;
}
}

public int theAnswer(anInt){
return anInt / divideByThisInt;
}

}

With this class, divideByThisInt should not be zero, because then theAnswer method would result in an error. So I make divideByThisInt private so that no one can make it zero.
In your program, I see no reason to make title private, because anyone can change it to anything. If I were you, I would either make it public and get rid of the get and set methods (making your program easier to read), or I would think about what kind of values I would not want title to have. For example, I think you probably don't want to have a title that is null or a string with no characters. So you should do this:

public void setTitle(String title) {
if (title != null){
if (!title.equals("")){
this.title = title;
}
}
}// end setTitle

Arulk: I am using regular text editor.

Roger: Thanks for the hint.

Kevin: Thank you for the advice and examples. I will redo based on your suggestion. One thing though. Because of these problems I have searched the internet for examples and such and found a program that mirrors my second code post. I corrected my code. Copied and ran their program which it did as one would expect. However, mine does not compile and run. I don't understand that. I have checked and double checked for errors. Case, etc. and I cannot find anything. Be that as it may, I will do what you are suggesting and see what happens. Thanks again all of you.

If you are still unable to solve your compilation problem, then post the code and error and we'll help.