Faking method chaining paradigm in Java

Dan — Thu, 19 May 2011 10:53:32 +0000

Method chaining is something I’m used to seeing in the C++ world, possibly because the programmers that live there are more used to passing around references. In Java I see this used much more infrequently and I’ve come to miss it. When adding new objects to some kind of array, for example, I find the following much more clear and concise than the non-chained alternative.

List list = new List();
//chained
list.add(new Thing().setValue(42));
//unchained
Thing thing = new Thing();
thing.setValue(42);
list.add(thing);

The major benefit being extra clarity for us humans. Too few Java programmers create their objects this way, which is a shame. The only change would be to return objects instead of voids in your setters, etc.

You can achieve a similar effect using instance initialisation blocks.

List thing = new List(){{
    add(new Thing(){{
        setValue(42);
    }});
}};

This really shines when you have a lot of setup to do on an object. Not only does this reduce code clutter, it means that you’re forced (if you stick to it) into keeping your intialisation code all in one place and you get nice hierarchic code style.

Daniel Jonathan McGreal

Faking method chaining paradigm in Java