Defining a data type

[Derek Szpik]

So I want to define a data type called Value. Value can only hold an integer in the range 0 to 65535 (inclusive), and must be able to be used in place of an int throughout my program. Do I just need to create a class like:
public int class Value{
...
}

and if so, what would I put inside to make everything work as I want?

[Garrett Rowe]

and must be able to be used in place of an int throughout my program.

Short answer... you cant. int' s in Java are a primitive type and therefore can't be subclassed, you can only create a subtype of a non-final, non-primitive type (hence you also can't subclass java.lang.Integer since it is final). Therefore you can't substitute any custom types for int.

Perhaps you could forgo int's altogether and only allow your types as parameters and return types in your problem domain. Or you could provide an easy way to convert from an int to a Value:

public static Value valueOf(int i) { //...}

public int toInt() {//...}

Or you could get really creative and subtype Number:

public class BoundedNumber<T extends Number> extends Number {
//...
}

[Derek Szpik]

hmm..that could pose a problem...

see, I need to define the following interface:

 public interface MySet{
boolean isIn(Value v);
void add(Value v);
void remove(Value v);
//and some other methods that don't require Value

and like I said above, a Value is a data type defined in the project outline as an integer between 0 and 65535 inclusive. Any other ideas on how to do this now that you know what it's for?

[Moojid Hamid]

Derek Szpik wrote:hmm..that could pose a problem...

How is that a problem? Since your interface is using Value not int, once you implement Value you can forget about int altogether.

[Derek Szpik]

well, that's my question, how do I create the data type of value? I don't know how to use the suggestions that Garrett made, so if anybody could provide me with a short section of code that creates value, that would be great.

[Moojid Hamid]

Derek Szpik wrote:well, that's my question, how do I create the data type of value?

Well in that case you will have to pick up a book on Java and read through the section that describes the concept of 'Class' and 'Object'.
Not to be rude but there are some rules of the forum including: Not A Code Mill,DoYourOwnHomework , and ShowSomeEffort .

When you have some specific questions everyone would be happy to help you lean.

[Rob Spoor]

You could always use char. Although you might think that char can be used for characters only, it is in fact a numeric type and compatible with int, and it has just the right range.

The only downside I see is that you will have to cast the char to int before printing:

char c = 65;
System.out.println(c); // A
System.out.println((int)c); // 65

[Campbell Ritchie]

Rob Prime wrote:You could always use char.

That was my first thought too. You can restrict the range if you accept an int as a constructor parameter

. . .

  /**
   * . . .
   *@param amount The value to be entered which must be within the range 0-65535 inclusive.
   *@throws IllegalArgumentException if the amount parameter is negative or above 65535.
   */
  public Value(int amount)
  {
     if (amount < 0 || amount > Character.MAX_VALUE)
        throw new IllegalArgumentException("The \"amount\" parameter must be in the range 0-"
               + Character.MAX_VALUE + " inclusive: " + amount + " not permissible");
     . . .

[Derek Szpik]

okay, thank you. I'll try a small program using chars ^.^

If that doesn't work, I figure I can always use plain int's, and just do a small check like

if(input>=0&&input<=65535){
//do whatever i need to with it
...}
else{
system.out.println("please input a valid number");}

That'll work, but it may cost me a mark or two (out of ~100) so I wanted to see if there was anything else. Thanks to all:)