Class 09-09 Notes CS 107
Friday, September 09, 2011 3:46 PM
Announcements: I updated the sample code you can use for program #2 Questions? Last Time: if statements Today: if statements, continued The switch statement: a shortcut to multiple if-else statements simple while loop break and continue statements if statements (continued from last time) [See other document under today's notes] switch statement Alternative to multiple if-else-if statements:
/* Illustrating the switch statement
Assume a program that prompts for your weight on earth and then gives you a menu of planet numbers to choose from for converting your weight to what it would be on that planet. One approach is to use multiple if statements: // Calculate weight on desired planet given earthweight and chosen planet if (menuOption==1) { planetWeight = earthWeight * 0.39; // Mercury } else if (menuOption==2) { planetWeight = earthWeight * 0.91; // Venus } else if (menuOption==3) { planetWeight = earthWeight * 0.38; // Mars } else { planetWeight = earthWeight - 1; // marketing ploy } we Instead, can use the "switch" statement shown below: */ switch ( menuOption) { case 1: planetWeight = earthWeight * 0.39; CS 107 Fall 2011 Page 1 // Mercury
*/ switch ( menuOption) { case 1: planetWeight = earthWeight * 0.39; // Mercury break; case 2: planetWeight = earthWeight * 0.91; // Venus break; case 3: planetWeight = earthWeight * 0.38; // Mars break; default: planetWeight = earthWeight - 1; // Earthweight - 1 // People like to think they're losing weight (marketing) break; } cout << " Your new weight is " << planetWeight "\n";
Note that switch cannot be used with variables of type String or float
Simple while loop: // e.g. count from 1 to 10 int counter = 1; while( counter <= 10) { System.out.println( counter); counter = counter + 1; //counter++ }
or
counter += 1
------------------------------------------------int counter = 3; ++counter increment the variable first, then use it vs. counter++ first use the variable, then increment it
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