scala vs java, performance and memory? [closed]

Answer 1

The Java example is really not an idiom for typical application programs. Such optimized code might be found in a system library method. But then it would use an array of the right type, i.e. File[] and would not throw an IndexOutOfBoundsException. (Different filter conditions for counting and adding). My version would be (always (!) with curly braces because I don't like to spend an hour searching a bug which was introduced by saving the 2 seconds to hit a single key in Eclipse):

List bigEnough = new ArrayList();
for(String s : array) {
  if(s.length() > 2) {
    File file = mapping.get(s);
    if (file != null) {
      bigEnough.add(file);
    }
  }
}

But I could bring you a lot of other ugly Java code examples from my current project. I tried to avoid the common copy&modify style of coding by factoring out common structures and behaviour.

In my abstract DAO base class I have an abstract inner class for the common caching mechanism. For every concrete model object type there is a subclass of the abstract DAO base class, in which the inner class is subclassed to provide an implementation for the method which creates the business object when it is loaded from the database. (We can not use an ORM tool because we access another system via a proprietary API.)

This subclassing and instantiation code is not at all clear in Java and would be very readable in Scala.