Unlock Groovy Maps: Quick Creation, Manipulation, and Powerful Operations

Creation

In Java a Map is typically created with Map<Integer, Integer> map = new HashMap();. Groovy simplifies this with literal syntax [k:v], allowing immediate initialization. Examples:

def map = [:]

def map = [a:32, b:32043]

Groovy uses java.util.LinkedHashMap by default; to use a different implementation such as java.util.HashMap, apply the as keyword:

def map = [a:32, b:32043] as HashMap

Adding Entries

Start with an empty map:

def map = [:]

Add a key‑value pair using bracket notation:

map["FunTester"] = 32432

Or use the dot operator, which treats the map like a bean:

map.FunTester = 32423

If the key is stored in a variable, you can use:

def map = [(DEFAULT_STRING):432423]
map[DEFAULT_STRING] = 324324

For merging maps, the + operator works:

def map1 = map + [c: 324]

Retrieving Values

Groovy offers two straightforward ways to get a value:

def map = [a: 32, b: 32043] as HashMap
output(map.a)
output(map["a"])

Deleting Entries

The - operator is overloaded to remove entries. It removes a key‑value pair only when both match:

def map = [a: 32, b: 32043] as HashMap
def map1 = map - [a: 32]
output(map1)

To delete multiple entries that satisfy a condition, use removeAll with a closure:

map.removeAll { it.value % 2 == 0 }

Conversely, retainAll keeps entries matching a condition:

map.retainAll { it.value % 2 == 1 }

Iterating

Iterate over each entry with each:

map.each {
    output("key:$it.key value:$it.value")
}

To also obtain the index, use eachWithIndex:

map.eachWithIndex { entry, i ->
    output("index:$i key:$entry.key value:$entry.value")
}

Filtering

Groovy provides three common APIs for filtering maps:

map.grep { it.value == 32 }
map.find { it.value == 32 }
map.findAll { it.value > 0 }

The findAll method returns a list of all matching entries, while grep is less frequently used due to limited IDE support.

These concise Groovy features help testers write shorter, more maintainable scripts without resorting to verbose Java boilerplate.