douglasgresham.co.uk

It looks like closures are making their way into Java 7.  Huzzah!  Since the Java guys are lavishing goodness upon us, I thought I’d put in a request to fix some of the petty grievances I have.  I’m going to ignore the core libraries for the purposes of this, as that’s a huge subject and libraries can be replaced (see the date/time API and Joda time).

Replace the ‘final’ keyword with the inverse, ‘mutable’

Mutable state is a necessary evil.  Immutable objects are simple to create and use, are automatically thread-safe and make testing much less painful, amongst other things.  Moreover, the fact that classes are overridable by default encourages people to use inheritance rather than lovely testable composition for code reuse.  Unfortunately though, nothing in Java is immutable by default, so you have to make a concious choice to do the simpler, better thing.  It’d be much better to have to declare a member or class mutable so that developers had to explicitly do it wrong.

Allow labelled parameters

public void drawSquare(int ~width x, int ~height y) {}
drawSquare(~width: 2, ~height: 3);
drawSquare(~height: 3; ~width: 2);

That way I don’t have to go and look up the API to see which way round they have to go.  Sure, leave the defaults the way they are – this clearly would have to be optional (maybe throwing a compile-time error if they’re wrong rather than swapping them?) – but it could help nip nasty logic bugs in the bud.

Allow default parameter values

public void foo(String bar = "douglas") {}

beats

public void foo(String bar) {}
public void foo() {
  foo("douglas");
}

in my book.  Syntactic sugar, but brevity and readability win out.

Implement arrays properly

byte[] a = {1, 2, 3};
byte[] b = {1, 2, 3};
a.equals(b); // will return false

Why?  Oh, I can use Arrays.equal()?  Fantastic, static calls, my favourite.  Oh, and there’s the whole nested array thing too, just for extra fun.

Allow switch statements on Strings

switch(myString) {
  case "foo":
    // some stuff
    break;
  case "bar":
    // other stuff
    break;
  default:
    // even more stuff
}

is more readable than

if ("foo".equals(myString)) {
  // some stuff
} else if ("bar".equals(myString)) {
  // other stuff
} else {
  // even more stuff
}

Syntactic sugar again – and also a possible source of bugs given casing and the Turkey problem – but I’d still like it.

Fix generics

Enough is written about this elsewhere.  Suffice to say, losing generic information at compile-time is a whole world of suck (it’s why you can’t have primitives as generics without boxing, for instance).

Swing should be banned.

Ok, I lied about ignoring libraries, but it cannot be said often enough that Swing is pure distilled evil.