COMP 110 Switch Statements and Loops Tabitha Peck M.S. February 6, 2008 MWF 3-3:50 pm Philips 367 1

Announcements Friday - No Lab! Bring questions on Project 2 Grades online next week 2

Questions? 3

Switch Statements switch (numOfSiblings) { case 0: System.out.print(“An only child”); break; case 1: System.out.print(“Just one you say”); break; case 2: System.out.print(“Two siblings!”); break; case 3: System.out.print(“Big family!”); break; default: System.out.print(“I don’t believe you”); break; } 4 Controlling expression int or char ONLY! Break statement Case label

Practice with Switch statements Write a switch statement that takes as controlling expression your year in college (as int) and outputs your year in college as freshman, sophomore, junior, senior, or super senior

Shorthand for if / else 6 if (n1 > n2 ) max = n1; else max = n2; max = (n1 > n2) ? n1 : n2;

Loops Loop - part of program that repeats Body - statements being repeated Iteration - each repetition of body Stopping condition 7

Types of Loops while Safest choice Not always most elegant do-while Loop iterates at least ONCE for Numeric computation changes by equal amount 8

While Loops count = 1; while (count <= num) { System.out.print(count + “, “); count++; } 1, 2, 3, 4, 5, 6, … num 9

While Loops Evaluate Boolean Expression Execute Body End loop true false 10

Do-while Loops count = 1; do { System.out.print(count + “, “); count++; } while (count <= num); 1, 2, 3, 4, 5, 6, … num 11

Do-while Loops Evaluate Boolean Expression Execute Body End loop true false 12 Execute Body

For Loops int count; // initializing action; boolean expression; update action for (count = 1; count <= num; count++) { System.out.print(count + “, “); } 1, 2, 3, 4, 5, 6, … num 13

For Loops Evaluate Boolean Expression Execute Body End loop true false 14 Execute Initializing Action Execute Update Action

Types of Loops while Safest choice Not always most elegant do-while Loop iterates at least ONCE for Numeric computation changes by equal amount 15

Bugs Problem with program preventing correct execution Infinite Loops!!!!!! 16

Infinite Loops count = 1; while (count <= num) { System.out.print(count + “, “); //count++; } 17

Infinite Loops count = 1; while (count <= num); { System.out.print(count + “, “); count++; } 18

Infinite Loops int count; // initializing action; boolean expression; update action for (count = 1; count >= num; count++) { System.out.print(count + “, “); } 19

Friday Help with Program 2 20