Groovy Goodness: Using The Switch Expression

In a previous (old) post we learned how Groovy supports different classifiers for a switch case statement. Since Groovy 4 we can use switch also as an expression. This means the switch statement returns a value without having to use return. Instead of using a colon (:) and break we use the -> notation for a case. We specify the value that the switch expressions returns after ->. When we need a code block we simply put the code between curly braces ({...}).

In the following example we use the switch expression with different case statements:

def testSwitch(val) {
    switch (val) {
        case 52 -> 'Number value match'
        case "Groovy 4" -> 'String value match'
        case ~/^Switch.*Groovy$/ -> 'Pattern match'
        case BigInteger -> 'Class isInstance'
        case 60..90 -> 'Range contains'
        case [21, 'test', 9.12] -> 'List contains'
        case 42.056 -> 'Object equals'
        case { it instanceof Integer && it < 50 } -> 'Closure boolean'
        case [groovy: 'Rocks!', version: '1.7.6'] -> "Map contains key '$val'"
        default -> 'Default'
    } 
}

assert testSwitch(52) == 'Number value match'
assert testSwitch("Groovy 4") == 'String value match'
assert testSwitch("Switch to Groovy") == 'Pattern match'
assert testSwitch(42G) == 'Class isInstance'
assert testSwitch(70) == 'Range contains'
assert testSwitch('test') == 'List contains'
assert testSwitch(42.056) == 'Object equals'
assert testSwitch(20) == 'Closure boolean' 
assert testSwitch('groovy') == "Map contains key 'groovy'"
assert testSwitch('default') == 'Default'

Written with Groovy 4.0.3.