Section 2, Thu July 3

Goals: 
 - Review homework 1
 - Review material introduced in lecture
 - Discuss homework 2
 - Continue talking about the development process

(1) Agenda
 -> Homework 1
 -  Lecture review
 -  Homework 2
 -  Working with code

(2) Homework 1
 - Solutions distributed in lecture
 - Coding question
   UWPerson p = new UWPerson("Sigurdsson", "Stefan", "stebbi");
 - Written assignment
    - Model, properties, responsibilities
    - Class, member variables, methods 
    - Questions? 

(3) Lecture review

From last week: 
 - Modeling
    - Objects
    - Properties
    - Property types
    - Property values
    - Object state
    - Responsibilities
    - Object relationships
 - Object design
    - An object has a value for each property
    - Properties are typed
    - Values must match the property types
    - The state of an object is the combination of its values

New concepts:
 - Invoke object responsibilities by sending messages
    - Queries
    - Commands
 - Classes are implementations of models in Java
 - In Java, objects are instances of classes
 - Two separate but identical objects of the same class *are different*
 - Boxes and bubbles; graphical notation for classes and objects
 - Object types are either rich or simple
 - The type of an object is its class
 - The int type is our first simple type
 - All classes are rich types
 - Instance variables
 - Methods
 - Constructors
 - Specification vs. implementation
 - Class definitions
    - Class name
    - The class keyword
    - "public" was not discussed in lecture
 - Class implementations
    - Surrounded by curly braces {}
 - Identifiers and keywords
 - Class and property identifiers -> use nouns
 - Method identifiers -> verb-based
 - Capitalization convention
 - Method specification 
 - "public" not discussed yet
 - Return type; the void keyword
 - Return statement
 - Parameters
 - Statement
 - Expression
 - Composing methods from statements and expressions
 - Arithmetic operators/expressions
 - Assignment expressions/statements
 - Variables and values; binding
 - Constructor syntax

(4) Homework 2
Questions to consider:
 - What is the relation between 
    - Models, objects, classes, class instances?
    - Properties, types, values, member variables, state?
    - Method parameters, member variables, local variables? 
 - What is a variable assignment?
 - What are the Java class libraries? 
 - What is a method return type? 
 - What is the signature of a method? 
 - What is the difference between a method returning a value, and 
   a program printing to the console output? 

(5) Homework 2
 - Questions about the PetSet and beastie code? 

(6) Working with code
 - Overview
    - Review from last week's section
    - New concepts: Libraries, API documentation
    - Coding example; the MutableString class

(7) Working with code
 - Process overview
    1 Run development environment
    2 Write source code in editor
    3 Save source files 
    4 Compile all source to create class files
    5 Run the class file with the main method
    6 Loop back to step 2 as necessary

(8) Libraries
 - Libraries are code written by others and useful to you
 - The code is usually not available
 - Instead documentation is made available
 - The standard Java class libraries are documented on-line at
   http://java.sun.com/docs/api/
 - API means Application Programming Interface

(The String class illustrates library use in the running example)

http://java.sun.com/j2se/1.4.1/docs/api/ -> java.lang.String

(9) Testing
 - The compiler detects syntax errors
 - Semantic errors are not detected by the compiler
 - You need to test your program to ascertain that it works as intended
 - The interactions pane is very useful for testing

(10) Debugging
 - If testing reveals flaws in the program you need to find and fix them
 - This process is called debugging 
 - Eniac story
 - If you don't learn how to test and debug you will not enjoy this course
 - Debugging is a main subject of next week's section

(11) Working with Code
 - Updated process overview
    1 Run development environment
    2 Write source code in editor
      Use libraries as much as you can
    3 Save and compile
    4 Run the class with the main method
      *or*
      test and debug using the interactions pane
    6 Loop back to step 2 as necessary