COMP 110 Branching Statements and Boolean Expressions Tabitha Peck M.S. January 28, 2008 MWF 3-3:50 pm Philips 367 1

Announcements Program 1 Due Today Hand in Pseudocode after class Program 2 Assigned Today Lab 2 Due Friday 2

Questions? 3

Today in COMP 110 Formatting decimals Review Worksheet If/Else statements Boolean Expressions 4

Formatting Decimals import java.text.*; DecimalFormat df = new DecimalFormat("0.00"); df.format(myVariable); Example code on class website 5

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); } 6

Integer division Double myDouble = (1 / 2) * 5.0; int i = 1 / 2; 0.5 O 7

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; 8

Flow Chart 9

Check time; if (time < 7am) { take bus; } else //time >= 7am { take subway; } Reach school; 10

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"); } } } 11 Start Prompt User for int Is user input greater than 5? Print: “small number” Print: “big number” YES NO

Java Comparison Operators ==Equal to !=Not equal to >Greater than >=Greater than or equal to <Less than <=Less than or equal to 12

Boolean Expressions True of False Example expressions 5 == 3; Variable <= 6; myInt != temp; if (boolean expression) {statements } 13

&& (and) What if you need multiple expressions to be true (expression) && (expression) && … Expressions go in ( ) Will only be true if ALL statements are true 14

|| (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 15

Gotcha == var1 = var2 (assignment statement) Error!!!!!!! var1 == var2 (boolean expression) Do NOT use == to compare Strings string1 == string2 //BAD string1.equals(string2); //GOOD 16

If Without Else You can use just an if statement if (boolean expression) { (statements) } the rest of your code 17

Nested If Else if (boolean expression) { if (boolean expression) { stuff goes here } else { more stuff } } else 18

Start Prompt User for int What is the integer? Print: “hello” Print: “how may I help you” inputInt > 1 inputInt == 0 Print: “how are you” inputInt == 1 19

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"); } } 20

Friday Recitation Bring Laptop Bring Book 21