摘要：
1. Variables (1) Three ways to define variables: 1) val refers to define an immutable variable; 2) var refers to define a mutable variable. 3) lazy va 阅读全文
摘要：
1. Scala is a contraction of "scalable" and "language". It's a fusion of objected-oritended and functional programming. 2. Compare Book class between 阅读全文