Object: *. 一個object最重要的兩個characteristics—state, behavior。(Real-World中的物件也是一樣的概念) *. State相當於一個物件所有的特徵。例如長度,高度,名稱,種類,顏色等等。 *. Behavior相當於這個物件能做的行為。例如跑,跳,說話,搖尾巴等等。 *. An object stores its state in fields (variables in some programming languages) and exposes its behavior through methods (functions in some programming languages). *. Hiding internal state and requiring all interaction to be performed through an object's methods is known as data encapsulation Class: *. Class相當於做出一個Object的藍圖或是模型,不是instance本身。 Inheritance: *. Common behavior can be defined in a superclass and inherited into a subclass using the extends keyword. Interface: *. Methods的集合,無implementation。 *. API: Application Programming Interface. Package: *. 用途相似的類別分門別類放在folder裡面。