继承：狗'是'动物。在Java中，这是通过 extends 关键字完成的。

Inheritance: Dog 'is an' Animal. In Java this is done by the extends keyword.

作文：狗'有'眼睛。在Java中，这是通过让Dog成为Eye的实例对象来完成的。

Composition: Dog 'has' Eyes. In Java this is done by having Dog an instance object of Eye.