The syntax of the if/else statement

if (booleanExpression) {statements}
[else if (booleanExpression) {statements}] ...
[else {statements}]

• Simplest statement to make decision
• Boolean expression appears within parentheses
• Space between keyword if and opening parentheses
• Execution always continues to next independent statement
• Use double equal sign (==) to determine equivalency

Pitfall: Misplacing a Semicolon in an if Statement

• No semicolon at end of first line of if statement
  • if (someVariable == 10)
  • Statement does not end there
• When semicolon follows if directly
  • Empty statement contains only semicolon
  • Execution continues with the next independent statement

Pitfall: Using the Assignment Operator Instead of the Equivalency Operator

• Attempt to determine equivalency
  • Using single equal sign
  • Rather than double equal sign
  • Illegal
• Can store Boolean expression's value in Boolean variable
  • Before using in if statement

Pitfall: Attempting to Compare Objects Using the Relational Operators

• Use standard relational operators to compare values of primitive data types
  • Not objects
• Can use equals and not equals comparisons (== and !=) with objects
  • To compare objects' memory addresses instead of values

Making Accurate and Efficient Decisions

• Series of if statements that determine whether:
  • Value falls within specified range
• Java programmers commonly place each else of subsequent if on same line
• Within nested if...else
  • Most efficient to ask most likely question first
  • Avoid asking multiple questions

Conditional (? :) Operator

It is a tertiary operator, which means that it takes three arguments.

expression1 ? expression2 : expression3

The expressions1 is a logical expression.

If expression1 = true, then the result of the condition is expression 2; otherwise, the result of the condition is expression 3