Suppose I have a list of Map such as: (Using json format just for demonstration) Now I want all the “id” values in a single String object, separated by a separator. For example, the above map should give me: Note: The order in which they are indexed in the list has to be maintained. I know I can d…
Tag: java-stream
Report on a multimap by producing a new map of each key mapped to the count of elements in its collection value
Imagine a multimap tracking persons, each of whom has a list of assigned tasks. How can I use streams to get a new map, mapping each Person to an Integer with the count of items found in their list of assigned tasks? How to get a result equivalent to this hard-coded map: I have been trying permutations of: An…
Merging multiple lists to one list of Objects in stream?
I have code like this. It uses JSoap library. I am getting titles, magnets, seeds, leechers (these two together as TorrentStats) from torrent site. Now I want to merge them inside one List, of course it’s pretty easy to do it in standard for loop but is there any way to map or flatmap them in stream? An…
Ignore exception in stream operations
Assuming you have an exception (checked/unchecked) in a stream operation and you want to ignore from now on this element. The stream must not be aborted, just ignoring elements throwing exceptions. I explicitly avoid saying skip, because it is a stream operation. So the example is using the map() operation fo…
How can I create a stream of objects?
Let’s say I have: and Then in a service, I have: It is not allowed to do the following: But ultimately, I have other classes that would share this interface and would want to do: Is there a way around this? Like using flatMap? (I noticed that if I have a wrapper class on a List of SomeClass objects, I
Exploring with Java streams required to read and convert the format of strings [closed]
Closed. This question needs debugging details. It is not currently accepting answers. Edit the question to include desired behavior, a specific problem or error, and the shortest code necessary to reproduce the problem. This will help others answer the question. Closed 2 years ago. Improve this question I am …
How To Store Values in Hashmap (comma Separated) with Same Key using Java Stream API?
I have a object named EntityObjectDTO like below: This AttributeType is an enum and can have values (RAW,REFERRED,ORIGINAL). I am trying to store all the attributes names and dataType into Hashmap of String key and value. This DataType can be duplicate as well. Input: Expected in a HashMap: {“Vehicle…
Convert generic arraylist to non-generic using Java 8 Stream
I have some old code I’m trying to streamline: I want to use the Java Stream API to simplify this. Here is my attempt: My understanding is that it would iterate through arr, typecast every object m to an int, and then collect it into a List. But my compiler says that the right-hand-side of the second li…
How can I use Java Stream to find the average of all values that share a key?
I’m having a lot of trouble with trying to average the values of a map in java. My method takes in a text file and sees the average length of each word starting with a certain letter (case insensitive …
How can I find the number of lines that contain a certain word in java using Java Stream?
My method would read from a text file and find the word “the” inside of each line and count how many lines contain the word. My method does work but the issue is that I need only lines that contain the word by itself, not a substring of the word as well For example, I wouldn’t want “th…