LECTURE NOTES
OCTOBER 6 2004

ASSIGNMENTS
10/8  CodeLab 5
10/18 Assignment 2

BOOLEAN EXPRESSIONS, CONT'D

Why?
- complex boolean expressions
What?
- operator precedence rules
How?
  - ! is considered a unary operator
  - relational operators come after additive operators
  - equality operators come after relational operators
  - && and || come after equality operators
  - operators with the same precedence are evaluated left-to-right

Why?
- mistakenly using a boolean for arithmetic
What?
- *arithmetic exception*

What?
- type mismatch
How?
  80 <= x < 90

USES OF BOOLEAN EXPRESSIONS

What?
- *defensive programming*
- perform tests to ensure robustness
  - e.g. performing tests in an instantiable class so that the client doesn't have to

What?
- *flag*

IF STATEMENTS

Why?
- default control flow is *sequential execution*
What?
- *control statement*
- *selection statement*
- *branching statement*
How?
- if-then statement
  - no then
  - only one statement in the block

What?
- diagram
How?
- diamonds for conditions
- rectangles for code blocks
- small circles where conditional flow becomes sequential again

Why?
- need more than one statement to be contingent upon the same condition
How?
- if statement
  - multiple statements in a block
  - requires curly braces
    - may use curly braces when only one statement (recommended)

What?
- placement of braces
How?
- consistency most important
    - if ( <boolean expression> ) {
          ...
      }
    - if ( <boolean expression> ) 
      {
          ...
      }

How?
- diagram if statement with multiple statements in a block

Why?
- want to present an alternative
What?
- if-then-else
How?
- then block and else block
- 0 or more statements in either block
- brace placement
    - if ( <boolean expression> ) {
          ...
      } else {
          ...
      }
      - consistent with Java code conventions
    - if ( <boolean expression> ) 
      {
          ...
      }
      else
      {
          ...
      }
    - if ( <boolean expression> ) {
          ...
      }
      else {
          ...
      }
- diagram