CS231 (Sp03) Review Topics for Exam 1

• What is the difference between an object and a class?
• How do you declare and create objects?
• How do you declare and create integers
• How do you send a message to an object?
• What does memory look like after each of the following steps and what is printed out?:

  Player p1, p2; 
  p1 = new Player(); 
  p2 = p1; 
  p2.setName("Elizabeth");
  p1.setName("Fred");
  p1 = new Player();
  p1.setName("George");
  System.out.println(p1.toString());
  System.out.println(p2.toString());
  

• What is garbage collection?
• Selection Statements
  • Patterns
    • guarded command pattern (if statement)
    • alternative action pattern (if-else if -else,…)
    • sentinel loop pattern (while statement)
    • counter loop pattern (while plus counter)
  • What are nested statements.
  • Review problems on pp 82-86.
• How are colors represented (i.e. what are RGB values?)
• What is inheritance? What is the superclass? What is the subclass? What does it mean to override a method?
• What code would generate a NullPointerException?
• What is basic structure of a class?
• Know how to write an entire class containing data variables, constructors, accessors, toString method, and other methods. What is the proper indentation structure.
• Variables can be data variables, local, parameters - what is the difference?
• When can variables have the same name and when can they not? When variables have the same name, how is the ambiguity resolved?
• What is "this"?

Additional Facts you need to know:

1. Information is stored in variables
2. Variables must be declared
3. To declare a variable you write a type followed by an identifier
4. Variables have 3 attributes: name, type, and value
5. The name and type are specified in the declaration
6. The value is variable (!) and is set only by assignment statements
7. Variables inside objects are called instance variables (because there is one for each instance of the class (i.e. one for each object of that type))
8. Instance variables are autoinitialized to 0
9. You may initialize them to something else by default
10. To access instance variables from outside an object (i.e. from another object), you use accessors.
11. There are two kinds of parameters, formal (variables), and actual (values).
12. When you define a method you declare formal parameters.
13. When you send a message, you include actual parameters (they have actual values)
14. Action is performed by sending messages to objects (including optional parameters if more information is needed)
15. You must create an object before you can send it messages.

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