How do I add multiple Groovy map entries without overwriting the current entries?

dictionary, groovy

Solution

You want something like Guava's MultiMap:

Multimap<String, String> myMultimap = ArrayListMultimap.create();

// Adding some key/value
myMultimap.put("Fruits", "Bannana");
myMultimap.put("Fruits", "Apple");
myMultimap.put("Fruits", "Pear");
myMultimap.put("Vegetables", "Carrot");

// Getting values
Collection<string> fruits = myMultimap.get("Fruits");
System.out.println(fruits); // [Bannana, Apple, Pear]

This guy makes a pure Groovy emulation of Multimap:

class GroovyMultimap {
    Map map = [:]

    public boolean put(Object key, Object value) {
        List list = map.get(key, [])
        list.add(value)
        map."$key" = list
    }
}

You can use `putAt` and `getAt` for syntatic sugar in map operations. You can also try a mixin in a map object.

He also uses Groovy with Guava's multimap:

List properties = ['value1', 'value2', 'value3']
Multimap multimap = list.inject(LinkedListMultimap.create()) {
    Multimap map, object ->
    properties.each {
        map.put(it, object."$it")
    }
    map
}
properties.each {
    assertEquals (multimap.get(it), list."$it")
}

Problem

My question with Groovy Maps. I've been searching for a way to programmatically add a new entry to a Groovy map without overwriting the current entry. For example ``` def editsMap = [:] lineEdits.flag.each { lineEdits_Flag -> editsMap.put('FlagId',lineEdits_Flag.id) editsMap.put('FlagMnemonic',lineEdits_Flag.mnemonic) editsMap.put('Action',lineEdits_Flag.action) println "editsMap: ${editsMap}" } ``` The first pass produces this map: editsMap: [FlagId:10001, FlagMnemonic:TRA, Action:review] But the second pass overwrites the first pass with: editsMap: [FlagId:10002, FlagMnemonic:REB, Action:deny] What I'm trying to do is create multiple entries within the one map. I need my map to populate something like this: ``` editsMap: [FlagId:10001, FlagMnemonic:TRA, Action:review] editsMap: [FlagId:10002, FlagMnemonic:REB, Action:deny] editsMap: [FlagId:10003, FlagMnemonic:UNB, Action:deny] editsMap: [FlagId:20001, FlagMnemonic:REB, Action:deny] editsMap: [FlagId:20002, FlagMnemonic:ICD, Action:review] editsMap: [FlagId:30001, FlagMnemonic:REB, Action:deny] editsMap: [FlagId:40001, FlagMnemonic:ICD, Action:review] editsMap: [FlagId:40002, FlagMnemonic:MPR, Action:review] editsMap: [FlagId:50001, FlagMnemonic:CPT, Action:deny] editsMap: [FlagId:60001, FlagMnemonic:DTU, Action:deny] editsMap: [FlagId:70001, FlagMnemonic:ICD, Action:review] editsMap: [FlagId:70002, FlagMnemonic:MPR, Action:review] ``` Once I have populated my map then I need to be able to find certain values in order to process a message. I believe that I can use something like: ``` def thisValue = appliedEditsMap[FlagId, '10001'] ?: "default" ``` to do a quick lookup. Can someone help me understand how to programmatically add values to a Groovy map without overwriting the values already in the map?

Original source