Trừu tượng hóa và Thiết kế Chương trình

Hiding the details

• Abstraction 抽象 means hiding details to focus on the main idea.
• You drive a car by the steering wheel and pedals — not by knowing the engine's internals.
• In code, abstraction lets you use something by what it does, not how.
• It's the single most important idea for managing large programs.

Procedural abstraction

• Procedural abstraction 过程抽象 packages a behavior into a method you call by name.
• Once written, average(scores) is used for its result — the code inside is hidden.
• The method name and parameters (its interface) are all a caller needs.
• This is exactly how you use library methods like Math.sqrt.

Decomposing a program into modules and sub-modules

Method decomposition

• Break a big problem into smaller behaviors, each its own method — method decomposition 方法分解.
• "Process an order" → checkStock(), chargeCard(), ship().
• Small, named methods are easier to write, test, and reuse.
• The main method then reads like a high-level summary.

Planning a class

• To design a class, decide what data it holds and what behaviors it offers.
• A Student has data (name, scores) and behaviors (addScore, average).
• Good design groups related data and behavior together.
• Planning first makes a program easier to build, read, and reuse.