The economics of duplication and abstraction in Java: knowledge duplication versus incidental (textual) duplication, what a shared abstraction costs, the wrong-abstraction failure mode, premature abstraction and speculative generality, essential versus accidental complexity. Use when deciding whether two similar pieces of code should be merged, whether a shared helper should be inlined back into its callers, when a utility has grown boolean parameters, or when reviewing code generalised for requirements that do not exist. Does not cover the smell catalogue (java-code-smells) or the mechanics of extracting and inlining (java-refactoring).
