I have a list of objects, and I need to group objects having status equal to my customizedStatusto a single customized one with count = sumOfSameObjectsCount . We have class MyObject Suggested implementation : Things work like a charm in case there are multiple objects with status equal to my customizedStatus…
Tag: java-stream
How to iterate over a Map to obtain a String of repeated Character Keys with Java 8
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
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 to Peek the Lowest elements from a List of sorted Streams continously
I started learning about Java Stream, and I am wondering is it possible to only peek the first element of the stream without retrieving it. For example, I have multiple streams, and each of them have integers that are sorted in non-decreasing order, and I want to get a sorted list of all integers, so I’…
Converting a Map into a sorted TreeSet using streams
The code is: Where the HashMap is There are 2 problems I run into using this code. First, for some reason Map.Entry::getValue runs into the error : The target type of this expression must be a functional interface I think the problem here is that the comparator cannot compare between two objects of type Vehic…
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 to write a method that takes in a List of Integer, Float, Double and calculate the average?
I am trying to write a method that takes in a list of numeric values – eg List<Integer>, List<Float>, List<Double> etc – and give me the average. These are the errors I get: Operator ‘+’ cannot be applied to ‘capture<? extends java.lang.Number>’, …
Aggregate multiple fields grouping by multiple fields in Java 8
In the Employee class below, I would like to get average salary, average bonus and average perks for all employees grouping by department, designation and gender and would like the result to be a List<Employee> with the aggregated values for salary, bonus and perks. What would be a clean way of doing th…
java.util.concurrent.TimeoutException Error
I am trying to create a function that will receive a stream of strings and it will return a sorted list of strings that meet all of the following criteria: They must contain the pattern The strings length must be equal to or greater than the min length number The strings length must be an even or odd number A…
Java 8 reduce method calls depending on a value
How to optimize method that returns the first non empty value returned of the checkN() methods and prevent the rest method calls and isEmpty() calls: #1 I thought of using stream filter and return first that has value, but it requires to call each check: SOLVED as M A suggested, finalized solution for me was:…