READING
Chapter 5
Section 1

- if statement
  - specify which block of code to execute
    - 0+ statements
- boolean expression
  - test condition
  - syntax
    if ( <boolean expression> ) 
       <then block>
    else
       <else block>
    - <boolean expression> is a conditional expression that is evaluated to either true or false
    - <then block> executed if <boolean expression> evaluates to true
    - <else block> executed if <boolean expression> evaluates to false
- relational operators
  <  less than
  <= less than or equal to
  == equal to
  != not equal to
  >  greater than
  >= greater than or equal to
- reversing relational operator and switching the if and then blocks results in equivalent code
  - reverse of < is >=, not >
- selection/branching statement
  - selects/branches to one alternative block for execution
  - diagram
    - have an arrow pointing to a diamond
    - put condition in a diamond
    - put each execution path in a box
    - draw arrows pointing from the condition diamond to the execution boxes
    - have the arrows come together to an empty circle
    - have an arrow pointing out of the circle
- blocks can contain more than one statement
  - single statement: exactly one statement
  - compound statement: zero or more statements
- multiple statements in a block must be surrounded with curly braces
  - otherwise compiler can't tell whether the second+ statements are part of the block
  - semicolons not necssary after right brace
  - can use braces even if block only has one statement
    - preferred by some programmers
      - easy to add temporary output
      - avoid dangling-else problem (discussed in 5.3)
  - placement of braces irrelevant to correct compilation
  - good style to do one of
    - if ( <boolean expression> ) {
          ...
      } else {
          ...
      }
      - consistent with Java code conventions
    - if ( <boolean expression> ) 
      {
          ...
      }
      else
      {
          ...
      }
    - if ( <boolean expression> ) {
          ...
      }
      else {
          ...
      }
    - consistency most important in your style choice
- if-then statement
  - syntax
    if ( <boolean expression> ) {
        <then block>
    }
  - call other version if-then-else statement
  - diagram
    - leave out second box and circle
  - not necessary because could simply do if-then-else with nothing in the else block
- instantiable class definitions should not crash even if the client doesn't perform the appropriate tests
  - class itself should contain necessary tests

Quick Check
1. a. valid
   b. invalid
   c. valid, but bad style
   d. valid, but bad style
2. a. if ( a < b) {
          x = y;
      } else {
      }
   b. if (a < b) {
      } else {
      }
   c. if ( a < b ) {
          x = y;
      } else {
          x = z;
      }