Head First Java

3. Primitives And References: Know Your Variables
Declaring a variable
variables must have a type
variables must have a name
“I’d like a double mocha, no, make it an int.”
Primitive Types
You really don’t want to spill that...
Back away from that keyword!
Controlling your Dog object
An object reference is just another variable value.
The 3 steps of object declaration, creation and assignment
There are no Dumb Questions
Java Exposed
Life on the garbage-collectible heap
Life and death on the heap
An array is like a tray of cups
Arrays are objects too
Make an array of Dogs
Control your Dog
What happens if the Dog is in a Dog array?
A Dog example
BE the compiler
Code Magnets
Pool Puzzle
A Heap o’ Trouble
The case of the pilfered references
Exercise Solutions
Puzzle Solutions
The case of the pilfered references

4. methods use instance variables: How Objects Behave
Remember: a class describes what an object knows and what an object does
Can every object of that type have different method behavior?
The size affects the bark
You can send things to a method
You can get things back from a method.
You can send more than one thing to a method
Calling a two-parameter method, and sending it two arguments.
There are no Dumb Questions
Reminder: Java cares about type!
Cool things you can do with parameters and return types
Encapsulation
Do it or risk humiliation and ridicule.
Hide the data
Java Exposed
Encapsulating the GoodDog class
How do objects in an array behave?
Declaring and initializing instance variables
The difference between instance and local variables
There are no Dumb Questions
Comparing variables (primitives or references)
BE the compiler
Mixed Messages
Pool Puzzle
Fast Times in Stim-City
Exercise Solutions
Puzzle Solutions

5. Writing a Program: Extra-Strength Methods
Let’s build a Battleship-style game: “Sink a Startup”
First, a high-level design
The “Simple Startup Game” a gentler introduction
Developing a Class
Brain Power
SimpleStartup class
Writing the method implementations
let’s write the real method code now, and get this puppy working.
Writing test code for the SimpleStartup class
There are no Dumb Questions
The checkYourself() method
Just the new stuff
There are no Dumb Questions
Final code for SimpleStartup and SimpleStartupTester
Prepcode for the SimpleStartupGame class
The game’s main() method
random() and getUserInput()
One last class: GameHelper
Let’s play
What’s this? A bug ?
More about for loops
Regular (non-enhanced) for loops
Trips through a loop
Difference between for and while
The enhanced for loop
Casting primitives
BE the JVM
Code Magnets
JavaCross
Mixed Messages
Exercise Solutions
Puzzle Solutions