Iterate through a hashmap with an arraylist?

Question

So I have a basic hashmap with an arraylist:

Map<Text, ArrayList<Text>> map = new HashMap<Text, ArrayList<Text>>();

Say I have a key value pair: Key: Apple, Value: orange, red, blue

I already understand how to iterate through to print the key and it’s values like so: Apple, orange, red, blue

but is there a way to break up the values/iterate through the inner ArrayList and print the key/value pair three separate times/print the key with each value separately like:

Apple orange
Apple red
Apple blue

That shouldn't be difficult, put your solution and we will help — niemar, Oct 06 '18 at 07:28
Possible duplicate of [Iterate through a HashMap](https://stackoverflow.com/questions/1066589/iterate-through-a-hashmap) — niemar, Oct 06 '18 at 07:29

score 3 · Answer 1 · answered Oct 06 '18 at 07:29

3

You could use a nested loop:

for (Map.Entry<Text, ArrayList<Text>> entry : map.entrySet()) {
    for (Text text : entry.value()) {
        System.out.println(entry.key() + " " + text);
    }
}

answered Oct 06 '18 at 07:29

Mureinik

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Doesn't this still just show the complete list of values per key? – Jane Dow Oct 06 '18 at 07:33
@JaneDow no, each row will have the key and one value from the array list. – Mureinik Oct 06 '18 at 07:34

score 3 · Answer 2 · answered Oct 06 '18 at 07:42

Using simple for loops, this would be:

for (Map.Entry<Text, ArrayList<Text>> entry : map.entrySet()) {
    for (Text text : entry.value()) {
        System.out.println(entry.key() + " " + text);
    }
}

Doing the same in a functional way:

map.forEach((key, valueList) ->
    valueList.forEach(listItem -> System.out.println(key + " " + listItem)
));

Iterate through a hashmap with an arraylist?

2 Answers2

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