Ch05 Visual Aids
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Transcript of Ch05 Visual Aids
© 2007 Lawrenceville PressSlide 1
Chapter 5Chapter 5
The if StatementThe if StatementChapter 5Chapter 5
The if StatementThe 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
For example, the statementif (x == 5) {
y = 20;}
assigns the value 20 to y only if x is equal to 5.
© 2007 Lawrenceville PressSlide 2
Chapter 5Chapter 5
Relational OperatorsRelational OperatorsChapter 5Chapter 5
Relational OperatorsRelational Operators
Operator Meaning== equal< less than<= less than or equal> greater than>= greater than or equal!= not equal
© 2007 Lawrenceville PressSlide 3
Chapter 5Chapter 5
The if-else StatementThe if-else StatementChapter 5Chapter 5
The if-else StatementThe 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.
© 2007 Lawrenceville PressSlide 4
Chapter 5Chapter 5
Nested if-else StatementsNested if-else StatementsChapter 5Chapter 5
Nested if-else StatementsNested 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.
© 2007 Lawrenceville PressSlide 5
Chapter 5Chapter 5
The if-else if StatementThe if-else if StatementChapter 5Chapter 5
The if-else if StatementThe 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.
© 2007 Lawrenceville PressSlide 6
Chapter 5Chapter 5
The switch StatementThe switch StatementChapter 5Chapter 5
The switch StatementThe 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;
}
© 2007 Lawrenceville PressSlide 7
Chapter 5Chapter 5
The Math ClassThe Math ClassChapter 5Chapter 5
The Math ClassThe 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
© 2007 Lawrenceville PressSlide 8
Chapter 5Chapter 5
Compound Boolean ExpressionsCompound Boolean ExpressionsChapter 5Chapter 5
Compound Boolean ExpressionsCompound Boolean Expressions
More than one Boolean expression in a single condition.
Formed using the logical And (&&), logical Or (||), or logical Not (!) operators.
© 2007 Lawrenceville PressSlide 9
Chapter 5Chapter 5
And Truth TableAnd Truth TableChapter 5Chapter 5
And Truth TableAnd Truth Table
AndAnd
Exp1Exp1 Exp2Exp2 ResultResult
True True True
True False False
False True False
False False False
© 2007 Lawrenceville PressSlide 10
Chapter 5Chapter 5
Or Truth TableOr Truth TableChapter 5Chapter 5
Or Truth TableOr Truth Table
OrOr
Exp1Exp1 Exp2Exp2 ResultResult
True True True
True False True
False True True
False False False
© 2007 Lawrenceville PressSlide 11
Chapter 5Chapter 5
Not Truth TableNot Truth TableChapter 5Chapter 5
Not Truth TableNot Truth Table
NotNot
ExpExp ResultResult
True False
False True
© 2007 Lawrenceville PressSlide 12
Short Circuit EvaluationShort Circuit EvaluationShort Circuit EvaluationShort Circuit Evaluation
• Java uses Short Circuit Java uses Short Circuit Evaluation to determine the Evaluation to determine the result of a compound Boolean result of a compound Boolean expressionexpression– Left side is evaluated firstLeft side is evaluated first
– If the result of the entire expression can be If the result of the entire expression can be determined by the value of the left determined by the value of the left operand, then no other operands will be operand, then no other operands will be evaluatedevaluated
© 2007 Lawrenceville PressSlide 13
Order of OperationsOrder of OperationsOrder of OperationsOrder of Operations
• Not (!) evaluated firstNot (!) evaluated first
• And (&&) evaluated secondAnd (&&) evaluated second
• Or (||) evaluated lastOr (||) evaluated last
© 2007 Lawrenceville PressSlide 14
Quarter 2 Drill # 4Quarter 2 Drill # 4Quarter 2 Drill # 4Quarter 2 Drill # 4
size=100size=100 weight=50weight=50 value=75value=75
1.1. size > 50 && weight ==50 t or size > 50 && weight ==50 t or f?f?
2.2. size > 50 || weight ==50size > 50 || weight ==50 t or f?t or f?
Which one of the above can be Short Which one of the above can be Short Circuited?Circuited?
© 2007 Lawrenceville PressSlide 15
Quarter 2 Drill # 4Quarter 2 Drill # 4Quarter 2 Drill # 4Quarter 2 Drill # 4
size=100size=100 weight=50weight=50 value=75value=75
1.1. !(value<75) !(value<75)
2.2. size >=100 || value >=100size >=100 || value >=100
3.3. Can #2 be short circuited?Can #2 be short circuited?
© 2007 Lawrenceville PressSlide 16
Quarter 2 Drill # 4Quarter 2 Drill # 4Quarter 2 Drill # 4Quarter 2 Drill # 4
size=100size=100 weight=50weight=50 value=75value=75
1.1. value < 100 && !(weight==50)value < 100 && !(weight==50)
2.2. !(size>100 && weight>50 && !(size>100 && weight>50 && value>75)value>75)
3.3. (value<125 || weight<76) && size==100(value<125 || weight<76) && size==100
© 2007 Lawrenceville PressSlide 17
Quarter 2 Drill # 4Quarter 2 Drill # 4Quarter 2 Drill # 4Quarter 2 Drill # 4
Write the following:Write the following:
1.1. Value not greater than 75 Value not greater than 75 or size not greater than 100or size not greater than 100
© 2007 Lawrenceville PressSlide 18
Chapter 5Chapter 5
The Math ClassThe Math ClassChapter 5Chapter 5
The Math ClassThe 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
© 2007 Lawrenceville PressSlide 19
Chapter 5Chapter 5
Flowchart SymbolsFlowchart SymbolsChapter 5Chapter 5
Flowchart SymbolsFlowchart Symbols
decisiondecision
© 2007 Lawrenceville PressSlide 20
Chapter 5Chapter 5
The RPS FlowchartThe RPS FlowchartChapter 5Chapter 5
The RPS FlowchartThe RPS Flowchart