Loop through Map in Groovy?

184
votes

I have a very simple task I am trying to do in Groovy but cannot seem to get it to work. I am just trying to loop through a map object in groovy and print out the key and value but this code does not work.

// A simple map
def map = [
        iPhone : 'iWebOS',
        Android: '2.3.3',
        Nokia  : 'Symbian',
        Windows: 'WM8'
]

// Print the values
for (s in map) {
    println s + ": " + map[s]
}

I am trying to get the output to look like this:

iPhone: iWebOS
Android: 2.3.3
Nokia: Symbian
Windows: WM8

Could someone please elaborate on how to do this??

4
dictionarygroovy
As you have seen in the answers, the problem is that iterating over a map gives you a collection of "Entries", you were assuming it would give you the keys and you would look up the values. If you wanted to do it that way, iterate over map.keySet() and the rest will work as you expected. - Bill K
It should work if you use s.key & s.value in your code inside for loop. - inblueswithu

4 Answers

343
votes

Quite simple with a closure:

def map = [
           'iPhone':'iWebOS',
           'Android':'2.3.3',
           'Nokia':'Symbian',
           'Windows':'WM8'
           ]

map.each{ k, v -> println "${k}:${v}" }
107
votes

Alternatively you could use a for loop as shown in the Groovy Docs:

def map = ['a':1, 'b':2, 'c':3]
for ( e in map ) {
    print "key = ${e.key}, value = ${e.value}"
}

/*
Result:
key = a, value = 1
key = b, value = 2
key = c, value = 3
*/

One benefit of using a for loop as opposed to an each closure is easier debugging, as you cannot hit a break point inside an each closure (when using Netbeans).

20
votes

When using the for loop, the value of s is a Map.Entry element, meaning that you can get the key from s.key and the value from s.value

16
votes

Another option:

def map = ['a':1, 'b':2, 'c':3]
map.each{
  println it.key +" "+ it.value
}