A common platform for concurrent bags, stacks and queues in .NET

September 26, 2016 Leave a comment

We’ve looked at the available concurrent collections in .NET before:

3 of these objects implement the same interface. Can you guess which three are similar in some sense? Stacks, bags and queues differ from dictionaries in that elements in those collections cannot be retrieved by an index of any sort. You can take/pop/dequeue the elements one by one but you cannot get to element #3 without first removing all elements before that.

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Filed under .NET, C# language features, Task Parallel Library Tagged with , , ,

Java 8 Date and time API: the Instant class

September 25, 2016 Leave a comment

The Date and time API in Java 8 has been completely revamped. Handling dates, time zones, calendars etc. had been cumbersome and fragmented in Java 7 with a lot of deprecated methods. Developers often had to turn to 3rd party date handlers for Java such as Joda time.

One of many new key concepts in the java.time package of Java 8 is the Instant class. It represents a point of time in a continuous timeline where this time point is accurate to the level of nanoseconds.

The immutable Instant class comes with some default built-in values:

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Java 8 Date and time API: the LocalDate class

September 24, 2016 Leave a comment

Introduction

The Date and time API in Java 8 has been completely revamped. Handling dates, time zones, calendars etc. had been cumbersome and fragmented in Java 7 with a lot of deprecated methods. Developers often had to turn to 3rd party date handlers for Java such as Joda time.

One of many new key concepts in the java.time package of Java 8 is the immutable LocalDate class. A LocalDate represents a date at the level of days such as April 04 1988.

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Converting a sequence of objects into a Lookup with LINQ C#

September 23, 2016 Leave a comment

A Lookup in .NET is one of the lesser known data structures. It is similar to a Dictionary but the keys are not unique. You can insert multiple elements for the same key.

Say you have the following object and collection:

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Messaging through a service bus in .NET using MassTransit part 4: dependency injection with StructureMap

September 22, 2016 Leave a comment

Introduction

In the previous post we saw how to publish messages with MassTransit. Our demo register customer command listener publishes a customer registered event that any interested party can sign up to. An advantage with the setup is that the publisher has no knowledge of the consumers, they are completely decoupled. The opposite and more frequent case is often a manager application that knows exactly which parties should be notified and sends them a message directly.

In this post we’ll diverge a little from messaging techniques and look at dependency injection instead. We’re inte particular interested in how to inject a dependency into a registered command or event consumer.

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How to warn the user if either CapsLock or NumLock are pressed in a .NET console application

September 21, 2016 Leave a comment

You’ve probably come across applications that warn you if the CapsLock button is pressed when typing a password. It’s a clever way to warn the user as passwords are normally not shown on the screen in plain text so it’s difficult to see what you’re typing. Similarly the NumLock button affects the behaviour of various keys on your keyboard.

Detecting whether those two special buttons are pressed is very simple in .NET console applications.

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Messaging through a service bus in .NET using MassTransit part 3: publishing messages to multiple consumers

September 20, 2016 3 Comments

Introduction

In the previous post we got our hands dirty and started coding a small demo application around MassTransit. We managed to send a message from a publisher to a consumer using the MassTransit/RabbitMq client library. We saw a very basic configuration of the bus control and how to register a consumer for a message type. The message type can by convention be an event or a command. Both are best encapsulated in an interface with get-set properties and separate naming conventions. Therefore commands and events are not some special C# language features in this case. Instead, they are basic terminology in the world of messaging. Our first example centred around sending a single command using a single queue.

In this post we’ll extend our demo to publishing a message that can be consumed by multiple receivers. The goal is to publish a customer registered event from the register customer command consumer. The event will be consumed by 2 receivers that the event publisher will not have any knowledge of.

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Filed under .NET, Messaging Tagged with , , ,

LINQ to XML techniques: adding a processing instruction

September 19, 2016 Leave a comment

In this post we saw how to add a declaration to an XML document. A well-formatted XML document starts with a declaration whose main function is to declare formally that the upcoming document is of the XML type. The XDeclaration object helps us to easily add a declaration to an XML document. Note that the XDocument.ToString method does not print the declaration for some reason so we need to print it separately if needed.

In this post we’ll see how to add a processing instruction to an XML document.

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Getting a result from a parallel task in Java

September 18, 2016 Leave a comment

In this post we saw how to execute a task on a different thread in Java. The examples demonstrated how to start a thread in the background without the main thread waiting for a result. This strategy is called fire-and-forget and is ideal in cases where the task has no return value.

However, that’s not always the case. What if we want to wait for the task to finish and return a result? Welcome to the future… or to the Future with a capital F.

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Filed under Async/Parallelism, Java Tagged with , , , ,

Running a task on a different thread in Java 8

September 17, 2016 Leave a comment

Occasionally it can be worth putting a task on a different thread so that it doesn’t block the main thread. Examples include a task that analyses heavy files, a task that sends out emails etc. If we put these tasks on a different thread and don’t wait for it to return a result then it’s called the fire-and-forget pattern. We start a new thread and let it run in the background. The task on the different thread is expected to carry out its functions independently of the main thread.

Let’s imagine that the following greetCustomer method is something we want to run on separate thread so that the main thread is not blocked:

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Filed under Async/Parallelism, Java Tagged with ,

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