JRJC - How To Use a Switch Statement

The general form of the switch statement looks like this:


    switch( expression )
    {
        case constant:
            stuff
            break;
        case constant:
            stuff
            break;
        case constant:
            stuff
            break;
        default:
            stuff
            break;
    }

You can have as many case statements as you want. You don't have to have a default statement if you don't want to.

expression is something that has to evaluate to something that is the same type as all of your constant values. After expression is evaluated, the resulting value is compared to each constant until a match is found and that stuff is executed. When break is encountered, the switch statement is exited.

If no match is found, the stuff under default is executed.

If no match is found and there is no default, then the switch statement is exited.

Example:


    switch ( dayOfWeek )
    {
        case 1:
            showMondayAgenda();
            break;
        case 2:
            showTuesdayAgenda();
            break;
        case 3:
            showWednesdayAgenda();
            break;
        case 4:
            showThursdayAgenda();
            break;
        case 5:
            showFridayAgenda();
            break;
        default:
            System.out.println("We don't work on weekends!");
    }

My wild theories that you don't need to know right now:

The switch statement is certainly better than a long series of "if" statements, but I have found that whenever I start to implement a switch statement, I can almost always find a better program design - usually by using an array or making a method that has more functionality. The only time that a switch statement is the right choice is when the evaluation leads to radically different functionality. And in those cases, a switch statement can almost always be replaced by polymorphism (a construct in object oriented programming)

For more information on switch statements, read page 175 of Just Java 1.2., or pages 71 through 73 in Just Java 2 (sixth edition).

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