One thing about Java

What's one thing that EVERY Java programmer has to know?  The kind of thing that drives you crazy if the supposed Java programmer didn't know it?

    Think of useing a usd, as a mental tax wright-off using it as toilet paper. To most people its worth the same amount as before worn down threw a dishwasher.

In general: decompose the logical units of your system into the smallest referentially transparent components possible, them implement them in modules. Global or local environments for sets of components (or inside components) might be mapped to monads. Use algebraic data types to describe core data structures. Share those definitions widely.

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ここに書いてね