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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. JAVA if Statement Syntax.

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selection if then else
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

java if statement syntax
JAVA if Statement Syntax
  • 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;

statement;

}

conditional operators
Conditional Operators
  • Relational Operators: < , > , >= , <=
  • Equality Operators: == , !=
selection examples
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!” );

slide5
else Statement
  • Syntax:
  • if (condition)
  • {
        • statement(s);//condition true
  • }
  • else
  • {
        • statement(s);//condition false
  • }
slide6
if-else Example
  • if (myGrade >= 60)
  • {
  • System.out.println(“You passed!” );
  • }
  • else
  • {
  • System.out.println(“How about them Cubs?” );
  • }
slide7
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
nested if statements
Nested if Statements

if (myGrade >= 80)

if (myGrade >= 90)

System.out.println(“You have an A!” );

else

System.out.println(“You have a B!” );

else

System.out.println(“We’ll give you a C.” );

if else cascaded
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!” );

else

if (myGrade > 70)

System.out.println(“You have a C!” );

else

System.out.println(“Oh-oh!” );

boolean type
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
logical operators
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
logical operators1
Logical Operators

if (numStudents > MIN && numStudents < MAX)

classRun = true;

if (numStudents > MAX || numInstructors == 0)

classRun = false;

operator precedence
Operator Precedence
  • ()
  • ! (not)
  • *, /, %
  • +, -
  • <, <=, >, >= (Relational Operators)
  • ==, != (Equality Operators)
  • && (Logical AND)
  • || (Logical OR)
  • = (ASSIGNMENT)
order of operations
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

multiple logical operators
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…..” );

switch statements
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
switch case example
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;

break;

case 5:

rate = BASERATE * 0.55;

break;

default:

rate = BASERATE;

break;

}

switch case example1
Switch Case Example

char menuItem;

String inputS;

System.out.print("Enter Menu Selection: “);

inputS = scan.next();

menuItem = inputS.charAt(0);

switch(menuItem)

{

case 'O':

//Code to Order Something

break;

case 'C':

//Code to Checkout

break;

default:

//Error Code

break;

}

announcements
Announcements
  • Quiz 1 This Thursday
  • 25 minutes
  • 5 % of Total Grade
  • Covers Everything through Lecture last Week
    • All Terms (Underlined Items)
    • Variable Declaration, Initialization, and Assignment
    • Constant Declaration
    • Expressions
    • Operators
    • Input (Scanner) and Output (System.out)
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