I have a Map shown below: I need to obtain the output: I can do it in normal process, but I want to do it in Java 8. Can you share some hints how to achieve this? Answer Here’s a couple of ideas on how to approach this problem using Java 8 streams. The overall idea: create a stream of
Tag: hashmap
Java Streams – group-by and return a Nested Map
my data is like this, my goal is put every unitId and value into a map like this, I already figure out two ways to achieve that, here is my code, and, First one more like write the processing manually, second one uses temporary lists which may not be necessary. Is there any direct or simple way to do this,
How can I collect two-dimensional Array into a Map<String, Set>?
I have an array of arrays of two strings. How can I collect the above array into a Map<String, Set<String>> whose key is the first element of each array and the value is a set of second elements of the array? So that I get following map? So far, I found I can classify the first element of each arr…
How can I use an If-statement inside the Collector?
The output I require is like this : The structure of this output is: Map<String, List<Pair<String, String>>> Where “Versions” is the key of the Map and [(“0.1″,”true”),(“0.2″,”false”),(“0.3″,”true”)] this is …
Compilation error while merging two Maps is being issued for Map.Entry::getKey
Whenever I use Map.Entry::getKey in my streams for my public methods, I get an issue around my method not being static. I even tried making my method static, and it didn’t work. Below is the compile error I am getting from using Map.Entry()::getKey() : My code Answer The method arguments are of type 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…
What is the time complexity of HashMap insertion and retrieval inside of a for loop?
I have written this code for an application but I’m having difficulty figuring out if its better than the legacy code (legacy code used one hashmap with List in every value). From what I understand, since Java 8 the insertion and retrieval from a Hashmap is O(log n) and the for loop is O(n) in my case. …
Hashmap using lists as a buffer
I need to create a hashmap that can store multiple values for one key, I know multimaps could do this but I also need to keep those value lists to a specific length. I need a each key to store a list of n values with those being the latest n values, i.e if i reached length n and I
Stream API how to modify key and value in a map?
I have a String – Array map that looks like this What I need to do is Create a new map, where key – only numbers extracted from String like this ( key -> key.replaceAll(“\D+”,””); Value – first value from array like this value -> value[0]; Filter an array so tha…
How to iterate through ArrayList values of HashMap?
A question from a total newbie. Sorry. I have this customersOrders HashMap that takes String as keys and ArrayList<Double> as values. I need to find the total sum of orders for each customer and the maximum total sum in order to find the biggest customer. How do I manage to do that using just nested For…