Welcome to northCoder

What is going on here? <R> Stream<R> map​(Function<? super T,​? extends R> mapper) Making sense of Java bounded wildcards, using Stream.map() as an example.

I recently saw !$:t in a tar command and had no idea what it was doing…

When you need to check which jar is being accessed to load a specific class…

A walkthrough of one way to launch a Docker container running a MySQL database server, and to enable access to the database from the host OS - for example, using JDBC.

An example of writing a potentially large amount of data directly to a zip file, item by item.

Session management in Java servlets.

VisualVM is a great tool for exploring Java applications and the JVM in which they are running. One area which has always been a bit overwhelming (to me) is the heap dump - a mass of raw information for millions of objects, which can be hard to sift through…

I have previously written about my wish to avoid being responsible for password management.  Here is the other side of the coin: Some code which (a) creates a hash for a new password, and (b) checks if a password is valid. Also included: A bonus digression on Java string immutability.

JSON is simultaneously straightforward and tricky…

In this walk-through I will take a look at AWS Cognito for user sign-up, password management and access controls, using a basic Java web application for demonstration purposes.