Null-safe access to properties

First I am going to show a nice side-effect of using properties with google-collections interface Function. Like many others I am annoyed to write code of the style

Bar getBarOfThing(Thing thing) {
  Bar bar = null;
  if (thing != null) {
    Foo foo = thing.getFoo();
    if (foo != null) {
      bar = foo.getBar()
    }
  }
  return bar;
}

All the null checks make it unreadable. And heaven forbid I forget one null test... BOOM! NPE! It's much nicer in SQL, for example, where everything's a bag, no results - no problem, join it with whatever you want, you'll just get an empty bag.

Now imagine that

foo = new Function<Thing,Foo>() {
  public Foo apply(Thing from) {
    return from.getFoo();
  }
}

and

bar = Function<Foo,Bar>() {
  public Bar apply(Foo from) {
    return from.getBar();
  }
}

Luckily google-collections have defined a @Nullable annotation and I am going to use it to differentiate between functions that can gracefully handle null (e.g. return some default value) and the ones that don't. Now I'm going to define a FunctionChain class, that provides me a fluent interface to chain the functions:

  FunctionChain<Thing,Bar> chain =
FunctionChain.<Thing>self().function(foo).function(bar); 

Which I can safely apply to any Thing, including null

  assertTrue(chain.applyTo(null) == null);