This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
this is used to indicate the instance variable which is a good coding style.
Your sample code has different variable names. But consider if you have something AB(int pi) Inside the constructor if you say pi, it will indicate the constructor argument, whereas this.pi indicates the instance variable