I have the following method: In this method, I pass a single menuUuid and then get combination of a single MenuPropertiesDTO and List<GroupExpDTO>. I want to pass a List<menuUuid> instead of a single menuUuid and then get the result according to the uuids in this list. However, I am confused if th…
Tag: java-stream
How to use stream to filter objects from HashSet that have empty value for certain fields?
I am looking for a way to filter only the Worker objects with a specific first name and empty lastName from the given HashSet. For example I want the code to return the record with firstName == scott and lastName == “”. Answer filter is a non-terminal operation and the stream would be processed on…
Java8 Streams: How to preserve the value before map to be accessed by collect/groupingBy functions
I’m using Java8 Streams to iterate through a list and for each of the element I invoke map and then I need to aggregate the results. My problem is that when I call groupingBy I also need to access the original object before calling map. Here is a snippet: The problem is with the call to Collectors.summa…
Get updated object after mapping by lambda expression
I have a list of objects as following, I want to update one of these objects and I have the following implementation This returns an object which satisfied with the condition based on filter. Unfortunately this is an not-up-to-date object! How can I get the updated object after mapping? Answer This is because…
Append list according to their size in Java
I am trying to append two list according to their size. With list with bigger size in front. I have few lists like this. List<Pair<Double, String>> masterList = new ArrayList<>(); and this is the working Java code that I tried first – with a simple if else loop: I am fairly new to the …
Iterating over and reducing values of a Java map via Stream API
Java 8 here. I have an array of Strings: Then I have a map where the keys are Strings (specifically, the same literal values as some of the animals in the array above), and the values are a count (representing the number of those animals): I am trying to figure out how to use the Stream API to iterate over
Create multiple Lists from one (Group List’s Objects by a specific field)
Given that I have the array of : gives me : I want to create a new array which is grouped by the 3rd parameter of surname object. So that my array becomes So that when we do .get(1) we would get object of kasis and samika. Need the help in respective to java 8. I heard that we can
stream filter return null findFirst getting exception
The following will throw an exception, if the personList is empty or the filtered result is empty: I get the following error: How to solve the error? Actually, I just expect it should return one object or null. Answer get will throw an exception if called on an empty Optional. Instead, you could use orElse to…
Java code refactor with stream Collectors.groupingby()
I try to get a Map with Collectors.groupingBy() but I have no idea how to create… I have a List from jpa jquerydsl the data is like [memberId=1, departmentId=1] [memberId=1, departmentId=2] [memberId=2, departmentId=3] [memberId=3, departmentId=4] this is my Member class I want to parse tuple list to me…
Java 8 edit stream elements
I need to filter and modify the values of the filtered object. The logic that must be filtered is given below. I have tried it like this. But how can we set the value of isUpdated = true using java 8? Answer Base on the logic given, findFirst should be used as you stop after the first instance is found.