Review Java concepts

General Programming Concepts:

   - objects - state, behaviour
   - input
   - output
   - variables
   - procedures
   - algorithms - small, explicit steps from description
   - compiling - what does it mean
   - executing - what does it mean

Java Specific Concepts:

   - compiling - how to compile
   - executing - how to compile
   - comments - //
   - main procedure - main flow of control
   - create variables
   - type - int, double, String
   - simple calculations - +,-,*,/
   - change variable values
   - writing output
   - reading input