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Simplify, simplify, simplify

Simplify the Semantics

• Guideline: Make object semantics as easy to understand as possible.
• Interfaces tell compilers and JVMs how to link to an object's methods.
• Interfaces can also say a lot to programmers about semantics: how to use an object.
• Make common things simple, rare things possible.
• Avoid modes.
• Apply the principle of least astonishment. (Semantic contracts should be unsurprising.)
• Be suspicious of urges to solve the general case rather than the specific problem.
• Occam's Razor: Get rid of anything that isn't absolutely essential or absolutely understood.

Why Simple Semantics?

• For people: Simple semantics makes objects easier to understand and use.
• Design by Contract and test suites help with "semantic discovery" and robustness.
• Design objects that communicate to programmers how to properly use them.
• Simple semantics has nothing to do with computers; it has to do with people communicating with people.
• Machine designers explaining to machine users how to use their machines (objects).