重读Think In Java -- Reusing Class

 @override 引用符号

如在基类里有一方法为 void f(int i)，你想在继承类中override这个方法，在打字时不小心把方法定义写成了void f(float i)，这时，编译器会认为你要overload方法f()，而不是overrid。为避免此类错误，可以在继承类中把需要override的方法标记为@override，当出现上述错误时，编译器会给出警告。

 

Composition or Inheritance

当不确定使用Composition or Inheritance时，就问一句“Do I need to upcast?”

 

The final Keyword

• using with data: The data can't be changed.The value of final variable can be set either at compile time or runtime.You can define  a final variable without setting a value,but u have to set value in the constructor. 
• using with methods: means the method can't be overridden.
• using with classes: means the class can't be inherited.