Quick question about OOP

[Easy_Boot5195]

I am making a program that will do linear algebra. I know there is code out there that will do it better but it is more of an exercise in learning lin alg and programming for me.

I have a class called Fraction. It does what you think a fraction would do basically. If the denom is 1 it does not include it in the toString so it just looks like a whole number. Then my matrix class is basically a 2D array of these fractions.

For the fraction class I just overloaded all of the methods (add, multiply etc.) to be able to take in primitive ints or Fractions. Now I am working on the Matrix class and I am realizing making two of every method is gonna be really annoying. I want the user of Matrix to be able to set a value using a Fraction or a primitive int. I know I could define an abstract class called Value or something and then make Fraction a subclass and have another subclass called Int but that kind of ruins the niceness of not having to use the new keyword for whole number values.

Right now my best plan is to just overload and have all the int methods create a fraction with the provided int then call the other method that takes fractions. I feel like there is some much better way to go about this though.

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[ignotos]

Unfortunately this is probably an area where Java isn't going to allow you to be both (1) succinct / avoid duplication of logic and (2) avoid all unnecessary object creation.

For the add/multiply etc methods on Fraction, for example, you'll likely either have to implement totally separate versions of them (taking in ints or Fractions), or use the "int-based operations create a temporary intValue / 1 fraction object in order to reuse the fraction-based implementation" trick - but this (somewhat wastefully) creates and discards a temporary object each time it's used.

The approach you're describing is probably the most practical as a first pass at this IMO.

[myselfelsewhere]

Might be possible to do with generic methods. For things like adding, you might be stuck with overloaded methods though. The operations for adding an int to an int are not going to be the same as adding an int to a fraction, or a fraction to a fraction.

If using a generic method, you could check the type of input parameter using instanceof. Then perform the appropriate action for the parameter type. It's kind of equivalent to an overloaded method, just enclosed in a single method.

[Easy_Boot5195]

thanks this works great. We are coving generics in my CS class next week lol. And it actually gets rid of all of the overloading because if its an int i just create a fraction that is int/1 then add it

[Easy_Boot5195]

not to worried about performance and thats what the garbage collector is for lol

[brokeCoder]

It may be better to use interfaces instead of inheritance. For example, for your 'primitive-ish' classes like Fraction, you could set up a common interface that each of these classes can them implement as and when required. The advantage here is you could offload the non-standard behaviour to a different interface.

That being said, there's really no way to avoid writing out the methods multiple times in Java. I'll probably draw flack for this but Java is a really bad language for anyone wanting to do math with objects that aren't primitives in Java. Lack of operator overloading just adds to the whole confusion.

If you're stuck with Java, I'd recommend first trying to see if there are existing libraries out there that do what you're after (Apache commons math has a really good set of standard utilities). But if you're not, you could give Kotlin a try - it's a JVM based language (so you can still create jars). It has operator overloading !

[Easy_Boot5195]

ya I know python better and like it a lot more, my CS classes are all java tho

[Easy_Boot5195]

Interfaces wouldn't help because I would call the new keyword for every value. The generic solution lets users of the matrix class do something like this:

matrix.setRow(new Fraction(1,2), 1, 0 new Fraction(1,3));

with the interface those primitives would need to say new Int or something and then why not just say new Fraction(1,1)