1. Conditional Control Structures Chapter 5

2. Goals and Objectives Understand conditional control structures. Demonstrate the use of decision structures to control the flow of a program. Demonstrate the use of decision structures to control the flow of a program. Generate random numbers. Write compound Boolean expressions Access methods in the Math class (Math.random(), Math.abs(), Math.pow(), Math.sqrt()). Create and modify solutions to problems. Create and modify solutions to problems. Develop code with correct and efficient use of conditional control structures. Understand and modify existing code.

3. The if Statement  Conditional control structure, also called a decision structure  Executes a set of statements when a condition is true  The condition is a Boolean expression that evaluates to True or False  For example, the statement if (x == 5) { y = 20; } assigns the value 20 to y only if x is equal to 5.

4. The if statement Beware of using the assignment symbol instead of the comparison symbol. Example if (x = 3) //This will not cause an error y = 4; Correct version: if(x ==3) y = 4;

5. Begin and End Symbols You don’t need a begin or an end symbol if you only have one statement for your if statement. if(x == 4) y = 6;

6. Relational Operators OperatorMeaning == equal < less than <= less than or equal > greater than >= greater than or equal != not equal

7. The if-else Statement Contains an else clause that is executed when the if condition evaluates to false. For example, the statement if (x == 5) { y = 20; } else { y = 10; } assigns the value 20 to y if x is equal to 5 or the value 10 if x is not equal to 5.

8. Nested if-else Statements  Should be indented to make the logic clear.  Nested statement executed only when the branch it is in is executed. For example, the statement if (x == 5) { y = 20; } else { if (x > 5) { y = 10; } else { y = 0; } } evaluates the nested if-else only when x is not equal to 5.

9. The if-else if Statement  Used to decide among three or more actions.  Conditions must be properly ordered for the statement to evaluate as expected. For example, the statement if (x < 5) { y = 20; } else if (x < 10) { y = 40; } else if (x < 15) { y = 80; } would give very different results if the conditions were ordered differently.

10. The switch Statement  Used to decide among three or more actions.  Uses an expression that evaluates to an integer.  The break statement moves program execution to the next statement after the switch.  The default code is optional and is executed when none of the previous cases are met: switch (numLegs) { case 2: System.out.println("human"); break; case 4: System.out.println("beast"); break; case 8: System.out.println("insect"); break; default: System.out.println("???"); break; }

11. The Math Class  Part of the java.lang package  The random() methods generates a double between 0 and 1.0. For example, double rNum; rNum = Math.random();  A random integer in a range is generated by using the expression: (highNum – lowNum + 1) * Math.random() + lowNum

12. Compound Boolean Expressions  More than one Boolean expression in a single condition.  Formed using the logical And ( && ), logical Or ( || ), or logical Not ( ! ) operators.

13. And Truth Table And && Exp1Exp2Result True False TrueFalse

14. Or Truth Table Or || Exp1Exp2Result True FalseTrue FalseTrue False

15. Not Truth Table Not ! ExpResult TrueFalse True

16. Logical Operators Example Compound Statement: –if ( x >= 3 && y = 3 && y < 6)

17. DeMorgan’s Law !(p || q)  !p && !q !(p && q)  !p || !q Example –!(x >= 3 && y = 3 && y < 10)Evaluates –(x = 10)

18. Short Circuit Evaulation AND && - If the first operand evaluates to False, the second operand will not be evaluated. OR || - If the first operand evaluates to True, the second operand will not be evaluated.

19. Order of Operations of Logical Operators !&&||

20. Order Of Operations () ++,--, unary !, type casting *, /, % +, - <,>,<=,>=,==,!=&&||

21. The Math Class  Part of the java.lang package  Methods include: abs(num) returns the absolute value of num pow(num1, num2) returns num1 raised to the num2 power sqrt(num) returns the square root of num, where num is a positive number

22. Flowchart Symbols decision

23. The RPS Flowchart