public boolean equals(Object other)

Question

This is for a Fraction program. I have private ints num and den, Fraction, and FractionInterface - the standard homework problem. I have done pretty much everything and now have been stuck for a few hours on the equals method. Since other is an Object, I can't equate it to Fraction. Here's what I have:

public boolean equals(Object other){        
     if (other == this){
         return true;
     } else {
         return false;
     }
}

This compiles but it gives incorrect results:

1/2 eq 1/2 = true
1/2 eq 1/2 = true
1/2 eq 1/2 = false
1/2 eq 1/2 = false

If I try other == Fraction, it doesn't compile. Thanks for any help!

Answer 1

You can test if other is an instance of FractionInterface and use a cast:

public boolean equals(Object other){        
     if (other == this){
         return true;
     } else if (other instanceof FractionInterface) {
         FractionInterface fOther = (FractionInterface) other;
         // compare numerator and denominator...
     } else {
         return false;
     }
}

Note that instanceof will be false if other == null, so there's no need for a separate null check.

Answer 2

Try this out:

First, cast the other object

Fraction otherFraction = (Fraction) other;

Then, determine the condition that the two fractions are equivalent. This will include some logic involving the comparing of numerator and denominators (expect to use getNum() and getDen() for the otherFraction.