Question

I have an old personal project written in Java 1.4 that I am porting to 1.5 (in which I am a still newbie) for version 2. Besides adding new features to it and refactoring code, I am also migrating to generic collections, annotations etc.

There is a particular piece of code that I don’t know how to change to 1.5 and don’t want to add a @SuppressWarnings on it. It goes like this:

if (value instanceof Comparable) {
  isMatch = (((Comparable) value).compareTo(selectedValue) == 0);
} else {
  //fallback to equals
  isMatch = selectedValue.equals(value);
}

It is just a simple comparison with an extensive match in compareTo() or defaulting to plain equals() if not a Comparable type.

I am getting a : Comparable is a raw type. References to generic type Comparable<T> should be parameterized warning.

How do I modify the above code to 1.5 and clear the warning. Or is there no choice but to add @SuppressWarnings?

Answer 1

I would rewrite this piece of code like this:

if (value instanceof Comparable<?>) { // <-- notice <?>
  // Declare local var and cast it here
  // You will incur warning, but it's localized to this one instance only
  //
  // Also not that this cast is safe as it matches the signature of Comparable
  // in Java 1.4
  @SuppressWarnings( "unchecked" )
  Comparable<Object> comp = (Comparable<Object>)value;

  // Now you can use compareTo
  isMatch = (comp.compareTo(selectedValue) == 0);
} else {
  //fallback to equals
  isMatch = selectedValue.equals(value);
}