Map<K,V>

A map associates or "maps" keys of type K to values of type V. Each key can map to at most one value -- a map cannot contain duplicate keys. See Maps for an overview of maps.

The following operations are supported for maps:

+ : (Map<K,V>, Map<K,V>) -> Map<K,V>

Concatenates two maps. If a key exists in both maps, the mapping from the right-hand side is used.

[] : (Map<K,V>, K) -> V

Given a map and a key, returns the value for the given key in the map, or null if the key is not in the map.

in, !in : (K, Map<K,V>) -> Boolean

Given a key and a map, returns true if the map contains the key and the corresponding value is truthy (e.g. not null, 0, or false).

The following methods are available for a map:

any( condition: (K,V) -> Boolean ) -> Boolean

Returns true if any key-value pair in the map satisfies the given condition. The closure should accept two parameters corresponding to the key and value of an entry.

containsKey( key: K ) -> Boolean

Returns true if the map contains a mapping for the given key.

containsValue( value: V ) -> Boolean

Returns true if the map maps one or more keys to the given value.

each( action: (K,V) -> () )

Invokes the given closure for each key-value pair in the map. The closure should accept two parameters corresponding to the key and value of an entry.

entrySet() -> Set<Map.Entry<K,V>>

Returns a set of the key-value pairs in the map. See Map.Entry for the operations available for each entry.

every( condition: (K,V) -> Boolean ) -> Boolean

Returns true if every key-value pair in the map satisfies the given condition. The closure should accept two parameters corresponding to the key and value of an entry.

isEmpty() -> Boolean

Returns true if the map is empty.

keySet() -> Set<K>

Returns a set of the keys in the map.

size() -> Integer

Returns the number of key-value pairs in the map.

subMap( keys: Iterable<K> ) -> Map<K,V>

Returns a sub-map containing the given keys.

values() -> Bag<V>

Returns a collection of the values in the map.

note

Maps in Nextflow are backed by the Java and Groovy standard libraries, which may expose additional methods. Only methods which are recommended for use in Nextflow are documented here.

Map.Entry<K,V>

A map entry is a key-value pair in a map. Map entries are returned by Map.entrySet():

def m = [a: 1, b: 2]
m.entrySet().collect { e -> "${e.key}:${e.value}" }   // -> ['a:1', 'b:2']

The following properties are available for a map entry:

key: K

The key of the entry.

value: V

The value of the entry.