Itereate HashMap with HashSet as values

Question

I've got HashMap with HashSet as value How to iterate over it ti reseive result like:

   key1
   value1
   value2
   value3
   ...
   key2
   value1
   value2
   value3
   key3
   ...

I have something wrong in my code:

Map<String, HashSet<String>> remarksMap = new HashMap<String, HashSet<String>>();
//...

Iterator<Map.Entry<String, HashSet<String>>> itr1 = remarksMap.entrySet().iterator();
Iterator<String> itr2 = itr1.next().getValue().iterator();

    while (itr1.hasNext()) {

        System.out.println(itr1.next().getKey());

        while (itr2.hasNext()) {
            System.out.println(itr2.next());

        }
    }

Currently receiving wrong result like:

key1
value1
value2
value3
key2
key3
key4
...

`itr2` never gets a second assignment... – nfechner Aug 22 '14 at 07:57 — nfechner, Aug 22 '14 at 07:57

score 2 · Answer 1 · answered Aug 22 '14 at 08:00

2

You don't need explicit Iterators to do this.

Here's a simplified nested iteration with fast-enumeration:

Map<String, HashSet<String>> remarksMap = new HashMap<String, HashSet<String>>();
for (String k: remarksMap.keySet()) {
    System.out.printf("%s%n", k);
    for (String v: remarksMap.get(k)) {
        System.out.printf("\t%s%n", v);
    }
}

answered Aug 22 '14 at 08:00

Mena

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Sorry about that: I just suggested an edit that was total rubbish. – chiastic-security Aug 22 '14 at 08:03
@chiastic-security no probs - intercepted ;) – Mena Aug 22 '14 at 08:04

score 1 · Answer 2 · answered Aug 22 '14 at 07:59

put that Iterator<String> itr2 = itr1.next().getValue().iterator(); into your loop like this:

Map<String, HashSet<String>> remarksMap = new HashMap<String, HashSet<String>>();
//...

Iterator<Map.Entry<String, HashSet<String>>> itr1 = remarksMap.entrySet().iterator();

while (itr1.hasNext()) {

    Map.Entry<String, HashSet<String>> entry = itr1.next();
    System.out.println(entry R.getKey());
    Iterator<String> itr2 = entry .getValue().iterator();

    while (itr2.hasNext()) {
        System.out.println(itr2.next());

    }
}

score 1 · Accepted Answer · answered Aug 22 '14 at 07:59

You initialize itr2 with the values of the first element of your map and not with the values of the current element. Adjust it like

Iterator<Map.Entry<String, HashSet<String>>> itr1 = remarksMap.entrySet().iterator();

while (itr1.hasNext()) {
    Map.Entry<String, HashSet<String>> entry = itr1.next();
    System.out.println(entry.getKey());
    Iterator<String> itr2 = entry.getValue().iterator();

    while (itr2.hasNext()) {
        System.out.println(itr2.next());
    }
}

score 1 · Answer 4 · answered Aug 22 '14 at 08:06

Check following code,

    Map<String,HashSet<String>> map = new HashMap<String,HashSet<String>>(); // Map with HashSet as value

    HashSet<String> hashset1 = new HashSet<String>();
    hashset1.add("Midhun");
    hashset1.add("Amal");
    hashset1.add("Ajith");

    HashSet<String> hashset2 = new HashSet<String>();
    hashset2.add("Sooraj");
    hashset2.add("Vinay");
    hashset2.add("Vishnu");

    // Putting data in to Map
    map.put("friends",hashset1);
    map.put("relatives",hashset2);

    for(Entry<String,HashSet<String>> mapEntry : map.entrySet()){
        System.out.println("Key :: "+mapEntry.getKey());
        for(String value : mapEntry.getValue()){
            System.out.println("Value :"+value);
        }
        System.out.println("===================");
    }

score 0 · Answer 5 · answered Aug 22 '14 at 08:00

Move your itr2 assignment to inside your itr1 while loop.

But be careful! Your System.out.println() in the outer loop grabs the next key, and your itr2 assignment currently does the same. Make sure you only call next() once each time you go through the loop, or you'll miss some keys.

Itereate HashMap with HashSet as values

5 Answers5