switch statements

You will not be tested on switch statements and the material on this page will not be covered on the AP Computer Science exam.

Objective #1: Be able to use the switch statement.

• switch statements are not covered on the Computer Science AP exam. However, they are handy to use so you should be familiar with them.
• The switch statement is a multiple-selection statement that allows you to model complicated logic similar to what an if else if else if else if else statement would allow. It chooses one of the "cases" depending on the result of the control expression. switch statements are often used with menus because it is easier to read a switch statement than a long if else if statement.
  
• Only variables with the int or char data types may be used in the control expression of a switch statements. Single quotes must be used around char variables.
  
• Example where the variable characterEntered is a char variable. Notice the required use of single quotes around the character values in each case.

  switch (characterEntered)
  {
  case 'A':
        System.out.println("You entered an A");
        break;
  case 'B':
        System.out.println("You entered a B");
        break;
  default:
         System.out.println("Illegal entry");
         break;
  }

• Example where the variable menuChoice is an int variable. Note that single quotes are NOT used around the integer values in each case.
  
  switch (menuChoice)
  {
  case 1:
       System.out.println("You entered menu choice #1");
       break;
  case 2:
       System.out.println("You entered menu choice #2");
       break;
  case 3:
       System.out.println("You entered menu choice #3");
       break;
  default:
       System.out.println("You failed to enter a valid menu choice");
       break;
  }
  
  
• The default case, if present, will result if neither of the prior cases apply. A default case is not required but it is good programming style to include one.
  
  
• The break statement must be used within each case if you do not want following cases to evaluate once one case is found. When the break statement is executed within a switch, Java will execute the next statement outside of the switch statement. However, sometimes it is desirable not to use the break statement in a particular case. Example:
  
  switch (donationLevel)
  {
  case 1:
     System.out.println("You donated over $1,000, you'll receive a free Wyo pocket watch.");
  case 2:
     System.out.println("You donated over $500, you'll receive a free Wyo 14K gold pen & pencil set. ");
  case 3:
     System.out.println("You donated over $250, you'll receive a free Wyo necktie.");
  case 4:
     System.out.println("You donated over $100, you'll receive a free Wyo bumper sticker. ");
     break;
  default:
      System.out.println("You are cheap and ungenerous.");
     break;
  }
  
  
• You can save redundancy in your code by placing the cases next to each other as in the following example.
  
  switch (number)
  {
  case 1:
  case 3:
  case 5:
  case 7:
  case 9:
       System.out.println(number + " is an odd number.");
       break;
  case 2:
  case 4:
  case 6:
  case 8:
       System.out.println(number + " is an even number. ");
       break;
  default:
       System.out.println(number + " is not a value between or including 1 and 9.");
       break;
  }
  
  
• According to our Coding Standards, you must include a blank line above your switch statement and one below it.