1. Selection (if-then-else)
Programming Has 3 Types of Control:
Sequential (normal): Control of Execution Proceeds One after the Other
Selection (if-then-else): Control Proceeds Dependent on Conditions
Iteration (looping): Control Repeated until Condition Met

2. JAVA if Statement Syntax
if (condition) statement;
If Condition Is True, Statement Is Executed
If Condition Is False, Statement Is Not Executed
If Multiple Actions Are Required for Statement, a Compound Statement Must Be Used:
if (condition) {
statement; }

3. Conditional Operators
Relational Operators: < , > , >= , <=
Equality Operators: == , !=
NOTE: Cannot use Equality Operators with Strings; must Use .equals() :
if (lastName.equals(“Li”))…

4. Selection Examples if (age < 30)
System.out.println( “You are very very Young”);
if (grade == ‘A’)
System.out.println(“Congratulations!” );
if (grade != ‘F’)
System.out.println(“You passed!” );
if (studentName.equals(“No Student”))
System.out.println(“Student Not Registered”);

5. else Statement Syntax: if (condition) { } else
statement(s); //condition true }
else
statement(s); //condition false

6. if-else Example if (myGrade >= 60) {
System.out.println(“You passed!” ); }
else
System.out.println(“How about them Cubs?” );

7. Compound Statements
Compound Statement: One or More Statements within a Set of Curly Braces
Must Use Compound Statement if More than One Statement Is Supposed to be under Control of if or else Conditional
Include Curly Braces after if so if other Statements Are Added in Future, Curly Braces Are Already There

8. Nested if Statements if (myGrade >= 80) if (myGrade >= 90)
System.out.println(“You have an A!” );
else
System.out.println(“You have a B!” );
System.out.println(“We’ll give you a C.” );

9. if/else (Cascaded) Sequence of if/else Statements Example:
if (myGrade > 90)
System.out.println(“You have an A!” );
else
if (myGrade > 80)
System.out.println(“You have a B!” );
if (myGrade > 70)
System.out.println(“You have a C!” );
System.out.println(“Oh-oh!” );

10. Boolean Type A Boolean Value Is One of Either “True” or “False”
In JAVA, Type boolean
Example:
boolean done = false;
. . .
if (currentLetter == ‘Z’)
done = true;
if/else Conditionals Must Evaluate to True or False, and Are Therefore Called Boolean Expressions

11. Logical Operators
A Logical Operator Is One Used to Further Specify True or False in an Expression
Connects Two or More Expressions Together
&& Is Logical “AND”
|| Is Logical ‘OR”
&&: Both Operands Must Be True for Entire Expression to Be True
||: Only One (or Both) of the Operands Must Be True for Entire Expression to Be True

12. Logical Operators if (numStudents > MIN && numStudents < MAX)
classRun = true;
if (numStudents > MAX || numInstructors == 0)
classRun = false;

13. Operator Precedence () ! (not) *, /, % +, -
<, <=, >, >= (Relational Operators)
==, != (Equality Operators)
&& (Logical AND)
|| (Logical OR)
= (ASSIGNMENT)

14. Order of Operations Precedence: Level of Importance of Operations
Multiplicative Operators Have Higher Precedence than Additive Operators:
*, /, % Higher
+, - Lower
Associativity: Order of Operation for Equal Level Precedence
Most Operators Have Left-to-Right Associativity
Use Parentheses to Force Differing Precedence of Operations

15. Multiple Logical Operators
if ( num1 > MAX || num2 == 0 && num3 == 0)
System.out.println(“ num1 is MAX or something is 0”);
System.out.println(“ I think…..” );

16. Switch Statements Also Called Switch/Case Statement
Just Case in Other Languages
Selects Among Several Different Actions
Can Only Select from Integer or Character
If an Integer Value Is Matched, Statements under Control of that Case Block Are Executed

17. Switch/Case Example int numPassengers;
System.out.print(“ Enter Passengers: “);
numPassengers = scan.nextInt();
switch(numPassengers) {
case 2:
rate = BASERATE * 0.80;
break;
case 4:
rate = BASERATE * 0.75;
case 5:
rate = BASERATE * 0.55;
default:
rate = BASERATE; }

18. Switch Case Example char menuItem; String inputS;
System.out.print("Enter Menu Selection: “);
inputS = scan.next();
menuItem = inputS.charAt(0);
switch(menuItem) {
case 'O':
case ‘o’:
//Code to Order Something
break;
case 'C':
case ‘c’:
//Code to Checkout
default:
//Error Code }

19. Announcements Exam 1 Next Week Thursday Everything through Lab 5
50 minutes
15 % of Total Grade
Covers Everything through Lecture this Week
Quiz 1 Topics (terminology, variables, constants, basics)
if-then-else
Compound statements
Relational operators
Logical operators
Switch/Case Statements