Self Aware Potato

PROBLEM: I have a method:  public String getChuckNorrisFact(); This method may also throw an exception, in my case IOException because this method does a service call to get a fact about Chuck Norris from web. I learned about  CompletableFuture  and now I am ASYNCING the shit out everywhere. Here is what I did: CompletableFuture<String> factFuture  = CompletableFuture.supplyAsync(() -> getChuckNorrisFact()); But the compiler tells me to handle or throw the exception, so I do this: CompletableFuture<String> factFuture2 = CompletableFuture.supplyAsync(() -> { try  { return getChuckNorrisFact(); } catch (IOException e ) { e .printStackTrace(); } }); Sadly there is still a compilation error in this. The supplier(lambda expression) in supplyAsync()  needs to return a string but there is no return statement if an exception occurs. So I do this: CompletableFuture<String> factFuture  = Compl

Singletons! Five different implementations of singleton design pattern in Java: Singleton class with eager initialisation of object. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 /* * The object is initialized while the class is being loaded * If your singleton class is not using a lot of resources, this is the approach to use * No option for exception handling while object creation. */ public class SingletonEagerInitialisation { private String name ; @Override public String toString () { return "SingletonEagerInitialisation [name=" + name + "]" ; } public String getName () { return name ; } public void setName ( String name ) { this . name = name ; } private static SingletonEagerInitialisation singletonObject = new SingletonEagerInitialisation (); public st

This post shows my new found love for CompletableFuture , lamdba expression and Streams API in Java. Problem: You do an async query on a table, get a ResultSetFuture object and need to populate a list of java objects representing a row in Cassandra table. A normal way to do this would be Assume: ResultSetFuture rsf = resultFromSomeTableQuery(); ResultSet rs = rsf.get(); //get ResultSet from rsf get all rows as list by rs.all() now for each Row in above list create a new object(POJO/java object representing table row) and populate the new object by calling Row.get(column index) for each column. This would lead to writing new code which does same task of converting ResultSetFuture to List of POJOs for each table query. Solution: I'll give my solution approach with an example

Java was a bit late in bringing Javascript's promise-like functionality. Future was there but wasn't as cool. So people at google made ListenableFuture . Now that java has CompletableFuture , it is common to run into problems like converting a ListenableFuture to a CompletableFuture. This can be because part of your older code uses ListenableFuture and now you have to compose your new logics utilising the newer and Java native technique. Following is one possible way to do it. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 public class FutureConverter { public static CompletableFuture toCompletableFuture ( ListenableFuture listenableFuture ) { final CompletableFuture completableFuture = new CompletableFuture (); Futures . addCallback ( listenableFuture , new FutureCallback () { public void onFailure ( Throwable throwable ) { completableFuture . completeException