The if Statement

1. Boolean Expression Then Block The if Statement if ( <boolean expression> ) { <then block> } if ( testScore >= 95 ) { System.out.println("You are a good student"); }

2. true testScore >= 95? System.out.println ("You are a good student"); false Control Flow of if • Praff … out to reality … If.java

3. if (testScore < 50) { System.out.println("You did not pass"); } else { System.out.println("You did pass"); } Boolean Expression Then Block Else Block The if-else statement if ( <boolean expression> ) { <then block> } else { <else block> }

4. true false testScore < 50 ? System.out.println ("You did pass"); System.out.println ("You did not pass"); Control Flow • Aaaieeeeooo … out to reality … IfElse.java

5. The Nested-if Statement • The then and else block of an if statement can contain any valid statements, including other if statements. An if statement containing another if statement is called a nested-if statement. if (testScore >= 50) { if (studentAge < 10) { System.out.println("You did a great job"); } else { System.out.println("You did pass"); } } else { //test score < 50 System.out.println("You did not pass"); }

6. inner if true false testScore >= 50 ? false true studentAge < 10 ? System.out.println ("You did not pass"); System.out.println ("You did pass"); System.out.println ("You did a great job"); Control Flow of Nested-if Statement • Zzzzzzatong … out to reality … NestedIf.java

7. if (testScore < 70) { messageBox.show("You did not pass"); messageBox.show("Try harder next time"); } else { messageBox.show("You did pass"); messageBox.show("Keep up the good work"); } Compound Statements • You have to use braces if the <then> or <else> block has multiple statements. Then Block Else Block • Always always always uses {}s, even if it’s not required

8. if (x < y) { if (x < z) { System.out.println("Hello"); } else { System.out.println("Good bye"); } } if (x < y) if (x < z) System.out.println("Hello"); else System.out.println("Good bye"); Matching else really means

9. if (x < y) { if (x < z) { System.out.println("Hello"); } } else { System.out.println("Good bye"); } Matching else if (x < y) { if (x < z) System.out.println("Hello"); } else { System.out.println("Good bye"); } means Kleeeptong … out to reality … MatchingElse.java

10. if ( <boolean expression> ) { … } else { … } if ( <boolean expression> ) { … } else { … } Style Guide Style 1 Style 2 • Always always always indent the true and false blocks

11. if (score >= 85) { System.out.println(”Grade is A"); } else { if (score >= 75) { System.out.println(”Grade is B"); } else { if (score >= 65) { System.out.println(”Grade is C"); } else { if (score >= 50) { System.out.println(”Grade is D"); } else { System.out.println(”Grade is N"); } } } } if - else- if

12. if (score >= 85) { System.out.println(”Grade is A"); } else if (score >= 75) { System.out.println(”Grade is B"); } else if (score >= 65) { System.out.println(”Grade is C"); } else if (score >= 50) { System.out.println(”Grade is D"); } else { System.out.println(”Grade is N"); } if - else- if • Ooorgh … out to reality … IfElseIf.java

13. Multiple method returns • A method can have multiple return statements. • If statements are often used to control which is used. • Bing-bada-boom ... out to reality ... IfReturn.java

14. Arithmetic Expression switch ( fanSpeed ) { case 1: System.out.println("That's low"); break; case 2: System.out.println("That's medium"); break; case 3: System.out.println("That's high"); break; } Case Label Case Body The switch statement switch ( <arithmetic expression> ) { <case label 1> : <case body 1> … <case label n> : <case body n> }

15. true N == 1 ? x = 10; false break; true N == 2 ? switch ( N ) { case 1: x = 10; break; case 2: x = 20; break; case 3: x = 30; break; } x = 20; false break; true N == 3 ? x = 30; false break; switch With break Statements • Vrootytoot … out to reality … Switch.java

16. switch ( binaryDigit ) { case 0: System.out.println("zero"); break; case 1: System.out.println("one"); break; default: System.out.println("That's not a binary digit"); break; } The switch Statement with default switch ( <arithmetic expression> ) { <case label 1> : <case body 1> … <case label n> : <case body n> default: <default body> } • Nic … out to reality … SwitchDefault.java

17. true N == 1 ? x = 10; false switch ( N ) { case 1: x = 10; case 2: x = 20; case 3: x = 30; } true N == 2 ? x = 20; false true N == 3 ? x = 30; false switch With No break Statements • Lapa-lapa … out to reality … SwitchFall.java