So i have these lines in a method – where Permission is a class and Name is a static inner class inside Permission Class, and getName() is a non-static method inside Permission class and getValues() is a static method inside Name class. The problem is getValues method returns a String Array. I am not ab…
Tag: java-8
Sorting based on order mentioned in a static map using java
How to sort a list of strings based on order mentioned in static map having item of list as key. List={“AU”,”I”,”U”, “O”, “A1”} Need to sort the above list of string using the below map which has …
Serial version uid in abstract exception class
I have a base custom exception class BaseException and several custom exceptions that extends BaseException I got a warning about serial version uid being not declared in the BaseException class. Is it needed in an abstract class? Is it a good practice? Is any way to get rid of the warning? Answer Yes, you ne…
parallelStream() java 1.8 vs 11
Consider the following code: When it is compiled and run with java 11, it returns the following: But with java 1.8, it returns different result: Why results are different? Answer Both results are consistent with the Java Memory Model. One possible ordering in which execution occurs is: but, because you don…
How to throw an Exception in a Consumer Java 8
Is there any way to throw an Exception while using a consumer in java 8? For example: This gives me a compiler error saying: Unhandled exception type Exception What is the correct way to throw an exception in this case? Answer Since Exception and its subclass (other than RuntimeException) are checked Exceptio…
CompletableFuture runAsync vs supplyAsync, when to choose one over the other?
What is the rationale for choosing one over the other? Only difference I could infer after reading the documentation is that runAsync takes Runnable as an input parameter and supplyAsync takes Supplier as an input parameter. This stackoverflow post discusses the motivation behind using Supplier with supplyAsy…
Creating a map from nested lists
Suppose there are 3 classes: Suppose there is a List of Level1 objects called initial state I want to create a map from initialList where: I am able to achieve this using for loops, but I want to achieve this in a more elegant way using Java 8 features (streams and the functions). I tried using Collectors.toM…
Multiple filters applied to a single list in Java 8+
How can be achieved to pass a “list of filters” to a stream in Java 8, instead of applying them individually as illustrated in the following example? https://howtodoinjava.com/java8/stream-multiple-filters-example/ The purpose would be to dynamically create a list of filters, one way would be to i…
Call custom static functions from filter and map in Java 8 – stream
I want to call method name nameStartingWithPrefix() which is inside filter and its definition will be in Filter class. All ArrayList describes in main(), but the list is not passed as in an argument, how can I call in List of names inside Filter.nameStartingWithPrefix(). Syntax is given like: names is name of…
Direct conversion from Collection to LongStream
I have a Collection<Long> (obtained from a Map<UUID, Long>’s values() method) and I would like to convert it into a LongStream. The simplest way I can think of is: However it strikes me that there should be a simpler way to obtain primitive streams from Collections of boxed equivalents. I ch…