Comparing objects and assigning the right value

Hello I am trying to compare the balance of two checking account objects for my class but I've run into a few problems.

 public int compareTo(Object other) {
  int otherBalance = 0;
  other = (Bankable) other;
  otherBalance = this.getBalance();
  if (otherBalance > getBalance()) {
     return otherBalance - getBalance();
  }
  else if (otherBalance < getBalance()) {
     return getBalance() - otherBalance;
  }
  else
     return 0;

}

The code above has a logic error such that otherBalance is equal to the wrong object's balance. This results in calls to this method always returning 0.

I've tried to correct this mistake by setting otherBalance = other.getBalance(); however this returns the compiler error cannot find symbol. If you could explain why that is I would appreciate it.

This line

other = (Bankable) other;

doesn't help you because the variable other is still of type Object, so you still can't call Bankable methods using it.

Create a Bankable variable instead.

Bankable that = (Bankable) other;

then you can call

int otherBalance = that.getBalance();

Replace other = (Bankable) other; with Bankable bankable = (Bankable) other; and otherBalance = this.getBalance();with otherBalance = bankable.getBalance();.

Looks like you have a couple issues:

• other = (Bankable) other does nothing, since other is always an Object type. Try creating a Bankable object that has getBalance:

  Bankable otherBankable = (Bankable) other;

• Once you have that you can fix the other issue, where you set otherBalance to this.getBalance(). It should be set to otherBankable.getBalance() instead.

Another solution that doesn't involve creating another object variable is to just cast when you want to get the balance:

otherBalance = ((Bankable) other).getBalance();

The "other" parameter for the compareTo method should be Bankable, not Object:

public int compareTo(Bankable other) { ... }

For this to work, your Bankable class should implement the Comparable<Bankable> interface - it sounds like you you may be missing the type parameter <Bankable> or you would be getting a different error. The Bankable class declaration should look like this:

class Bankable implements Comparable<Bankable>

Finally, with the way you have implemented compareTo, it can only return 0 or a positive number. It must be possible for compareTo to return negative numbers - that's how it can tell you that the current "this" object should come before the "other" object. A correct and compact way to implement compareTo is:

public int compareTo(Bankable other) {
    return Integer.compare(this.getBalance(), other.getBalance());
}