iterate over a map instead of a list

Question

My code for presenting results looks like this:

    private void presentResult(List<Long> result) {
    if(result.size() == 0) {
        System.out.println("No matching values for the provided query.");
    }       
    for(String s : result) {
        System.out.println(s);
    }
}

But I want to return a hashmap instead of a list so I want it to be like this:

    private void presentResult(Map<LocalDate, Long> result) {
    if(result.size() == 0) {
        System.out.println("No matching values for the provided query.");
    }       
    for(Map<LocalDate, Long> s : result) {
        System.out.println(s);
    }
}

But then I get this error: "Can only iterate over an array or an instance of java.lang.Iterable" How can it be solved?

You're asking how to **iterate** a map, not how to return it. — khelwood, Mar 04 '20 at 15:58
Does this answer your question? [How do I efficiently iterate over each entry in a Java Map?](https://stackoverflow.com/questions/46898/how-do-i-efficiently-iterate-over-each-entry-in-a-java-map) — Alexandru Somai, Mar 04 '20 at 16:01
You are talking about the input parameter of the method, not the return type. Better is to follow some good tutorial and learn the language vocabulary. — Neetesh Bhardwaj, Mar 04 '20 at 16:02

score 0 · Accepted Answer · answered Mar 04 '20 at 15:58

0

I think you're asking how to iterate a map, instead of list. You can iterate the map like this:

for (Map.Entry<LocalDate, Long> entry : result.entrySet()) {
    System.out.println(entry.getKey() + " " + entry.getValue());
}

answered Mar 04 '20 at 15:58

Oleksi

12,947
4
56
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score 0 · Answer 2 · answered Mar 04 '20 at 15:58

You need to use result.entrySet(). That returns a Set<Entry<LocalDate, Long>>>, which is iterable (Map isn't).

Your loop would look like this:

for (Entry<LocalDate, Long> s : result.entrySet()) {
    System.out.println(s.getKey() + " - " + s.getValue());
}

score 0 · Answer 3 · answered Mar 04 '20 at 15:59

0

You should use entrySet of map.

for(Map.Entry<LocalDate, Long> s : result.entrySet) 
{ 
    System.out.println(s.getKey()); 
    System.out.println(s.getValue());
}

answered Mar 04 '20 at 15:59

xialeistudio

26
2

iterate over a map instead of a list

3 Answers3