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.

Answer 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
    }