Flow Control and Exception Handling - switch Statement

Syntax (JLS §14.10)

    switch( expression ) {
        case value1:
            statement1;
            break;
        case value2:
            statement2;
            break;
        case value3:
            statement3;
            break;
        ...
        case valuen:
            statement n;
            break;
        default:
            statements;
    }

• transfers control depending on the value of an expression
• the type of the expression must be byte, char, short or int
• case labels must be constant expressions capable of being represented by the switch expression type

    char c;
    
    switch( c ) {
        case 'a':
        case 'b':
        case "c":       // String, not character!
        case 'd':    
    }

• no two case constant expressions may be the same
• the default case does not have to be at the end of the code block
• if no case matches the expression, the default case will be executed
• if break is omitted between case blocks the code will fallthrough, continuing to execute statements until a break statement or the end of the switch block is encountered

Example Code

• TestSwitch.java

Tips

• you do not have to have a default statement
• the default statement can appear anywhere in the construct, does not have to be last

Traps

• using an expression vs a value promotable to int
• duplicate case values
• case statements with wrong type
• missing break statements