Lecture 1

Object Orientation:

• a development strategy
• systems should be built from a collection of reusable components called objects
• a network of intelligent agents, communicating via messages
• why: much easier to build and debug than procedural code
• main attributes: operations not data
• Object≠data+methods
  • encapsulation
    • data is private
    • implementation is hidden
  • objects are defined by what they do, not what they contain
• rules
  • don't ask object for data, but rather ask for work to do over that data (change a class's implementation without affecting any of objects using that class)
  • Open-closed principle: software modules should be open for extension and closed for modification

Development Methodologies:

• Heavyweight process: when the entire problem is fully defined before development begins
• Lightweight process: when the problem definition changes as development is in progress
• Agile process: when requirements change

All large computer programs are nondeterministic: OOP doesn't eliminate the problem but makes it manageable.

Java Virtual Machine:

• "write once, run anywhere"
• when code is compiled, it produces a byte code instead of a binary executable
• JVM allows the byte code to run on any operating system with a JVM
• runs slower than compiled native languages

Lecture 2: Classes