I have the following data stored as lists: I need to group it as follows What I have tried is the following: But this doesn’t give the desired result. Answer Here’s how you can apply nested groupingBy To collect it in the order encountered, you can use a LinkedHashMap, Result:
Tag: treemap
Converting List to TreeMap java lambda
I’m trying to convert a List<String> to a TreeMap<Long, CustomClass> The key is the same as the list items but just parsed to Long, the value is just a call to new CustomClass(). How can I achieve this using lambda functions? the above code errors out, with the following error, Answer For ex…
How to match equals() and hashCode in streams?
I have a stream where I am aggregating some data like this: The problem is that by adding this comparator I am braking the contract between hashCode() and equals() and at the end I have duplicate keys: Has anyone some ideas how can I fix this? Or is there a way to sort the final object ( Map<String, Map<…
putting value in Treemap understanding issues
I was running through a leetcode problem. and found a solution in the discussion section problem- https://leetcode.com/problems/stock-price-fluctuation/ solution- but I do not understand the following parts. if someone could explain that would be great Answer To solve the problem you need to know how often th…
How to iterate from a given key in Java TreeMap
I have a TreeMap, and want to get a set of K smallest keys (entries) larger than a given value. I know we can use higherKey(givenValue) get the one key, but then how should I iterate from there? One possible way is to get a tailMap from the smallest key larger than the given value, but that’s an overkil…
Comparing the contents of two Treemaps
I have two TreeMaps that I want to compare. I currently have it written down like below but I feel like this could be written more efficiently. I tried looking in to comparators, but I don’t think that’s something I can use for my use-case. The maps are Treemaps because the key must be case-insens…
How to sort the keySet() of a TreeMap with keys containing number?
I’ll briefly describe what I did and then show how the result I got, differs from my desired result. Thanks in advance for any suggestions. Java code was created in a java online compiler and is executable there without error message in any case. Java online compiler, which was used Short description: I…
How treemap handles case of putting key on same index?
I tried out following code: public static void main (String[] args) throws java.lang.Exception { // sorting based on number of dots Map map =new TreeMap((o1, o2) -&…
Why do I get an error when entering child classes to a TreeMap defined for their parent? [closed]
Closed. This question is not reproducible or was caused by typos. It is not currently accepting answers. This question was caused by a typo or a problem that can no longer be reproduced. While similar questions may be on-topic here, this one was resolved in a way less likely to help future readers. Closed 2 y…
How to write custom comparator in java?
I want to store key-value pairs in TreeMap and sort the entries based on the value of key as per the following logic: “type” (case insensitive) key should be at first. the key start with “metadata” (case insensitive) should be at last in ascending order rest of the keys(case insensitiv…