Sorting Arrays

[Chris Rothgeb]

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

 

 
  

[Stevi Deter]

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 ]

[Chris Rothgeb]

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
    

[Bear Bibeault]

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.

[Chris Rothgeb]

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.

[Roger Chung-Wee]

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

[arulk pillai]

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

[Kevin Tysen]

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

[Chris Rothgeb]

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.

[Roger Chung-Wee]

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