Vanilla Java

  Event-driven microservices  can be straightforward to describe before they are implemented, tested and maintained. They are also highly responsive to new information in real-time, with latencies in Java of below 10 microseconds 99.99% of the time, depending on the functionality of the small, independently deployable microservice.    In this introductory article, we use an example  event-driven   Hello World  program ( a programming paradigm where the program flow is determined by events)  to step through   behaviour-driven   development , where we describe the behaviour the business needs first as test data and write a very simple  microservice  which turns input events like this. say: Hello World Into outputs like this, by adding an exclamation point say: Hello World !  # <- adds an exclamation point All the code for this example is  available on GitHub . When modelling Event-Driven systems, a useful pattern is ...

  Behaviour Driven Development (BDD) and Event-Driven Architecture (EDA) work well together as they complement each other’s strengths and weaknesses. Using both can result in a shorter time to market for new functionality and a more maintainable system. Behaviour Driven Development  encourages a common language between users and developers in describing requirements in a form the users can understand but can also automatically be checked as the application is developed and maintained. BDD increases the inclusion of users, focuses on requirements capture and maintains the development velocity as the application increases in complexity. Figure 1. Behaviour Driven Development for the high level with Test Driven Development for the low level   Table 1. Pros and Cons of Behaviour-Driven Development   Event-Driven Architecture  models interactions between services as events. Events are facts about something that happened to represent a state change, such as an order p...

These wise words were written by François Fénelon, a writer and theologian living during the 17th century. This is an article summarising different approaches to the development of IT solutions. Learn why the above quote is very relevant for developers in the 21st century.   Business-driven development  is a meta-methodology for developing IT solutions that directly satisfy  business requirements . This leads to increased flexibility and shorter turnaround times when changing the business and adapting the IT systems.    This is achieved by adopting a  model-driven  approach that starts with the business strategy, requirements and goals and then refines and transforms them into an IT solution. Due to the alignment of the business and IT layers, it is possible to propagate changes in the business automatically to the IT systems.    This is partially replaced by Domain-Driven Design and Behaviour Driven Development in Agile terminology.  ...

My previous post with Eight Core Java Questions was popular so I created nine more. Please join the discussion of the answers for these questions on Twitter 1. Comment on this question How many elements does this set have? Set set = new HashSet(Arrays.asList( -0, +0, -0L, +0L, -0F, 0F, -0D, 0D, 0xF, 0xD, 0x0.DP+0)); System.out.println(set.size()); 12 1 6 9 2. Comment on this question This compiles in Java 17 due to static int[] a(int[]... a)[] { return a; } static final int one = a(new int[0]).length; // 1 It confuses the compiler It’s a static method Backward Compatibility JEP 747 3. Comment on this question The code below prints "23 & 52" the following due to System.out.println( new BigDecimal(2.008f).toString().length() + " & " + new BigDecimal(2.008).toString().length()); A bug in Java 23 The randomness of floating-point Length of the mantissa Magic numbers ...

Please join the discussion of the answers for these questions on Twitter The answers to each question can be combined for a bonus question at the end. 1. Which of these is NOT a means of communicating between processes in Core Java. Comment on Twitter UDP Pipes/Files Pass by reference TCP 2. Which of these methods of copying an object is the LEAST efficient? Comment on Twitter Java Serialization clone() Copying field by field Using a builder 3. Which of these is the lowest amount of time Comment on Twitter A micro-day A nano-year 0.001 seconds A millsecond A million nanoseconds 100 microseconds 4. This loop doesn’t throw an Exception Comment on Twitter List<String> words = new ArrayList<>(Arrays.asList("one,two,three".split(","))); for (String word : words)   if (word.startsWith("t"))     words.remove(word); Because It’s in proportional font A thread s...

Apache Kafka is a common choice for inter-service communication. Kafka facilitates the parallel processing of messages and is a good choice for log aggregation. Kafka claims to be low latency, high throughput . However, is Kafka fast enough for many microservices applications in the cloud? When I wrote Chronicle Queue Open Source my aim was to develop a messaging framework with microsecond latencies, and banks around the world have adopted it for use in their latency-sensitive trading systems. In this article, I will describe how Kafka does not scale in terms of throughput as easily as Chronicle Queue for microservices applications. As a teaser, I will show you this chart showing that Chronicle Queue is around 750 times faster even for lower throughput. Visualising delay as a distance In order to illustrate the difference, let me start with an analogy. Light travels through optic fibre and copper at about two thirds the speed of light in a vacuum, so to appreciate very short de...