COMP 110Branching Statements and Boolean

Expressions

Tabitha Peck M.S.

January 28, 2008

MWF 3-3:50 pm

Philips 367

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Announcements Program 1 Due Today

Hand in Pseudocode after class

Program 2 Assigned Today

Lab 2 Due Friday

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Questions?

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Today in COMP 110 Formatting decimals

Review Worksheet

If/Else statements

Boolean Expressions

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Formatting Decimals import java.text.*;

DecimalFormat df = new DecimalFormat("0.00");

df.format(myVariable);

Example code on class website

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Review Worksheet

public class MyProgram{

public static void main(String[] args) {

String myString = “This is a string”; int len = myString.length(); System.out.print(“the length is “ + len); String shortString = myString.substring(10);

} }

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Integer division

Double myDouble = (1 / 2) * 5.0;

int i = 1 / 2;

0.5

O

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Classes Suppose that mary is an object of class Person, and suppose

that increaseAge is a method of class Person that uses one argument, an integer. Write the invocation of the method

increaseAge for the object mary using the argument 5.

mary.increaseAge(5);

Person mary = new Person;

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Flow Chart

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Flow Chart

Check time;

if (time < 7am){

take bus;}

else //time >= 7am{

take subway;}

Reach school;

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Java Example import java.util.*;

public class FlowChart { public static void main(String[] args) { System.out.println("Give me an integer:"); Scanner keyboard = new Scanner(System.in); int inputInt = keyboard.nextInt(); if( inputInt > 5) { System.out.println("Big number"); } else { System.out.println("Small number"); } } }

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Start

Prompt User for int

Is user input greater than 5?

Print: “small number”

Print: “bignumber”

YESNO

Java Comparison Operators

== Equal to

!= Not equal to

> Greater than

>= Greater than or equal to

< Less than

<= Less than or equal to

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Boolean Expressions True of False Example expressions

5 == 3; Variable <= 6; myInt != temp;

if (boolean expression){ statements }

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&& (and)

What if you need multiple expressions to be true

(expression) && (expression) && … Expressions go in ( )

Will only be true if ALL statements are true

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|| (or)

What if you need ONE expression to be true out of many expressions

(expression) || (expression) || … Expressions go in ( )

Will be true if ONE expression is true

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Gotcha == var1 = var2 (assignment statement)

Error!!!!!!! var1 == var2 (boolean expression)

Do NOT use == to compare Strings string1 == string2 //BAD

string1.equals(string2); //GOOD

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If Without Else

You can use just an if statement

if (boolean expression)

{ (statements) }

the rest of your code

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Nested If Else

if (boolean expression){

if (boolean expression) { stuff goes here }else { more stuff }

}else

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Start

Prompt User for int

What is the integer?

Print: “hello” Print: “how may I help you”

inputInt > 1inputInt == 0

Print: “how are you”

inputInt == 1

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import java.util.*;

public class FlowChart { public static void main(String[] args) { System.out.println("Give me an integer:"); Scanner keyboard = new Scanner(System.in); int inputInt = keyboard.nextInt(); if ( inputInt == 0) System.out.println(”hello");

else if ( inputInt == 1)System.out.println(”how are you");

else System.out.println(”how may I help you");

} }

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Friday

Recitation

Bring Laptop

Bring Book

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