I am trying to generate a HashSet containing unique Employee instances. Uniqueness should be established based on the object properties. The problem is that I end up with having duplicates. Note that Employee class is provided by a framework, and it’s not possible to provide custom implementations for e…
Tag: hashset
I have a HashSet pre. Is there a fast way to do HashSet PreIDs = for each x do x.getID in Pre? (in Java)
There is a class Prerequisite, it has a method getID(). Instead of doing is there a more efficient or more concise way to call a method over a HashSet? Answer As @ernest_k said, there isn’t any more efficient way in my opinion too. But we can write that whole logic in one line as below (if you are using…
What is the purpose of placing a HashSet inside of a HashMap?
For example: private HashMap<Integer, HashSet> variableName; I understand that HashMap implements Map and doesn’t allow duplicate keys and HashSet implements Set and doesn’t allow for duplicate values, but what is the purpose of placing a HashSet inside of a HashMap? Do they not achieve simi…
Ambiguity in a CodeForces Problem – usage of HashSet Vs LinkedHashSet
I was solving a Codeforces problem yesterday. The problem’s URL is this I will just explain the question in short below. Given a binary string, divide it into a minimum number of subsequences in such …
Use HashSet to weed out duplicate values. List returns either empty or returns duplicate values
I am trying to remove duplicate values from an ArrayList using HashSet, so that city names aren’t returned more than once if they are the same… The List comes back either empty or still shows duplicate values. Was hoping someone could tell me where the error is in my code, so that no duplicate values ar…
Is it possible that TreeSet equals HashSet but not HashSet equals TreeSet
I had a interview today and the person taking my interview puzzled me with his statement asking if it possible that TreeSet equals HashSet but not HashSet equals TreeSet. I said “no” but according to him the answer is “yes”. How is it even possible? Answer Your interviewer is right, th…
Why can’t custom comparator be used with hashSet to check duplicate objects
I want to use a custom comparator to filter duplicate objects from a HashSet. In the Mobile class, I have defined a non-static nested Comparator class for comparing. The criterium which is used by this comparator is the id field of the Mobile object. Even though it works perfectly for a TreeSet, Eclipse shows…
How to find an object in a Set of custom objects
The code below contains a Set of CustomObjects. I am trying to search an object in it. I’ve overridden equals() method to match it with a specific field, am not able to understand why is it not able to find it. “XXtNot FoundtXX” is getting printed instead of “Found!!” import java…