Android: Compare two Maps keys, if keys are equal create new object

Question

I have two LinkedHashMap<String, MyType> where keys can be common (say key from first map can be "key" and key from second map can be also "key". I need to compare this two maps and when keys are equal I want create new object where firsMapEntry.getValue() secondMapEntry.getValue() are attributes of new object [ new MyObject(firsMapEntry.getValue(), secondMapEntry.getValue()) ]. Maps are in Collection so I iterate through collections.

Here's my source:

firstIterator = firsCollection.iterator();
secondIterator = secondCollection.iterator();

    while (firstIterator.hasNext() && secondIterator.hasNext()) {
        Map<String, MyType1> firsMap = firstIterator.next();
        Map<String, List<MyType2>> secondMap = secondIterator
                .next();

        firstMapIterator = firstMap.entrySet().iterator();
        secondMapIterator = secondMap.entrySet().iterator();

        while (firstMapIterator.hasNext() && secondMapIterator.hasNext()) {
            Map.Entry<String, MyType1> firstEntry = ((Map.Entry<String, MyType1>) firstMapIterator.next());
            Map.Entry<String, List<MyType2>> secondEntry = ((Map.Entry<String, List<MyType2>>) secondMapIterator.next());


           // Here I was trying to compare keys but unsuccessfuly

          // if keys are equal create new object

        My Object object = new MyObject(firsEntry.getValue(),
                    secondEntry.getValue());
                      Map<String, MyObject> map = new LinkedHashMap<String,MyObject(); map.put("key", object);

        }
    }

Return type of method is List<Map<String, MyObject>>. I don't know if my method is effecient, but how to compare two keys and create new object from values. Every help will be appreciated. Thank you.

Where are you comparing the keys in your above code? Have you removed that piece and replaced with the comments? — Swapnil, Jan 06 '13 at 18:30
Yes where are comments, there I want compare keys. I had sth. like if ( firstkey.equals(secondKey) { ... but as result a I got always only one Map — Martin, Jan 06 '13 at 18:31
What if you have map entries `1, 2` in the first map and `2, 1` in the second? You use `LinkedHashMap` so it appears that insertion order is significant to you; hence the question — fge, Jan 06 '13 at 18:41

score 1 · Accepted Answer · edited May 23 '17 at 12:12

1

Map.Entry has a method called getKey() , use this to get the key.
Since your key is a String use , Object.equals() to compare them , do not use '==' ,so:

    if(firstEntry .getKey().equals(secondEntry .getKey())){
    //they are equal
    }
else{
    //they are different
    }

edited May 23 '17 at 12:12

Community

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answered Jan 06 '13 at 18:33

wtsang02

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I've done it but as result I've had only one Map, I've tought that it doesn't work. Maybe there's a bug somewhere. – Martin Jan 06 '13 at 18:41
Thank you guys finally I've found mistake in source. – Martin Jan 06 '13 at 20:53

Android: Compare two Maps keys, if keys are equal create new object

1 Answers1