How is refactoring like throwing out the rubbish?

In these green days, you no longer just throw out your rubbish. You rinse, separate, sort and then throw.

A process, not dissimilar to refactoring.

Some code goes into your grey, household waste bin. This is the stuff that was written before the scope of the project was finalised. It has normally been written quickly, doesn't always fit the spec, and is often bug-ridden. It can't be recycled. Just bin it.

But hopefully most of your code will end up in the blue bin. This is the stuff that can be re-used - sometimes with no changes - but usually needing a bit of washing and sorting.

You can help the process by building modular code with good clean interfaces early on in development.

In this green age, filling your blue bin and recycling old code as much as possible is essential. And this can be helped by building modular code - with good, clean interfaces - early on in the development.