hashmap with regexp as key, groovy/java - regex

Question

I`ve encountered a problem:
Is it possible, to use regexp as a key in hashmap?
For example:
def unitsMap=[
(~/(?i).*ABC.*nM.*/):'AAA',
(~/(?i).*DEF.*nM.*/):'DDD'
]
println unitsH3HashMap['ABC (122344345P)']
Of course, that returns null value.
Best regards

Answer 1

No, but you can use it in a switch:
def unitsMap(key) {
switch(key) {
case ~/(?i).*ABC.*/: return 'AAA'
case ~/(?i).*DEF.*/: return 'DDD'
}
}
println unitsMap('ABC (122344345P)')

Answer 2

In order to get what you want you would have to write your own implementation of Map that uses pattern matching to perform getAt, putAt, contains, etc. However, it seems to me that the algorithmic complexity for lookups in such a scenario would always be O(n). Not very good compared to HashMap (O(0)) or TreeMap (O(log n)).
#tim_yates 's solution solves the raw outline of the problem as presented, but would not allow you to add new keys (cases) on-the-fly, as would your original desired code. If on-the-fly changes to your "map" are not important to you, then you should definitely use his solution (which I will endorse by giving it +1 now). If not, the you might be able to adapt his code to generate and invoke a script from a Map that will do what you desire.
This script:
// generate unitMapper
def generateUnitMapper(baseMap) {
def script = '''{ key ->
switch (key) {
'''
script += baseMap.collect { k, v ->
""" case ~/${k}/: return '${v}'
"""
}.join("")
script += ''' default: return null
}
}
'''
}
// notice this map is just using the regular expression STRINGS as keys,
// not the PATTERN objects from the original poster's code
def starterMap = [
/(?i).*ABC.*[\dA-Z]+.*/:'AAA',
/(?i).*DEF.*[\dA-Z]+.*/:'DDD'
]
def closureScript = generateUnitMapper(starterMap)
def unitsClosure = Eval.me(closureScript)
println closureScript
println unitsClosure('ABC (122344345P)')
println()
// regenerate map and closure and rerun
def changedMap = [ /ABC .*/:'000' ] + starterMap
closureScript = generateUnitMapper(changedMap)
unitsClosure = Eval.me(closureScript)
println closureScript
println unitsClosure('ABC (122344345P)')
Yields this output:
{ key ->
switch (key) {
case ~/(?i).*ABC.*[\dA-Z]+.*/: return 'AAA'
case ~/(?i).*DEF.*[\dA-Z]+.*/: return 'DDD'
default: return null
}
}
AAA
{ key ->
switch (key) {
case ~/ABC .*/: return '000'
case ~/(?i).*ABC.*[\dA-Z]+.*/: return 'AAA'
case ~/(?i).*DEF.*[\dA-Z]+.*/: return 'DDD'
default: return null
}
}
000