Insert a non-existent value into a Map in Java 8

February 21, 2015 Leave a comment

Consider the following Employee class:

public class Employee
{
    private UUID id;
    private String name;
    private int age;

    public Employee(UUID id, String name, int age)
    {
        this.id = id;
        this.name = name;
        this.age = age;
    }
        
    public UUID getId()
    {
        return id;
    }

    public void setId(UUID id)
    {
        this.id = id;
    }

    public String getName()
    {
        return name;
    }

    public void setName(String name)
    {
        this.name = name;
    }    
    
    public int getAge()
    {
        return age;
    }

    public void setAge(int age)
    {
        this.age = age;
    }
}

Let’s put some Employee objects into a hash map:

Read more of this post

Filed under Java Tagged with , ,

The ‘if’ preprocessor directive for the compiler in C# .NET

February 20, 2015 2 Comments

You can decorate your C# source code with “messages” to the compiler. There are a couple of predefined preprocessors that the compiler understands.

A common scenario is when you’d like to run some part of your code in Debug mode but not in Release mode or any other Build type. The following method shows the ‘if’ and ‘elif’ preprocessors:

Read more of this post

Filed under .NET, C# language features Tagged with ,

Using Amazon Elastic MapReduce with the AWS.NET API Part 2: the cluster startup GUI

February 19, 2015 1 Comment

Introduction

In the previous post we went through a quick introduction of Amazon Elastic MapReduce. In this post we’ll very shortly describe Hadoop first. Then we’ll log into EMR and go through the long section in the GUI which you fill in to specify the details of your cluster.

If you are entirely new to Hadoop and Amazon Web Services then you’ll see a lot of new tools mentioned on this page that hide some complex applications with their own learning curves. So get ready for a lot of reading and research. It can be of great help if you have people in your organisation who already have some prior knowledge of AWS when starting with EMR.

Read more of this post

Filed under .NET, Amazon, Big Data Tagged with , , , , ,

Extending class definitions with partial classes in C# .NET

February 18, 2015 Leave a comment

The ‘partial’ keyword helps you divide your classes into multiple files within the same namespace. One obvious usage of partial classes is to split the definition of a large type into smaller chunks. You cannot just use the partial keyword with classes but methods as well.

The partial classes will reside in two – or more – different cs files in the same namespace. Say you have a partial Customer class in the project-name/domains folder:

Read more of this post

Filed under .NET, C# language features Tagged with , ,

How to find various machine-level system information with C# .NET

February 17, 2015 Leave a comment

The Environment class holds a range of properties that help you describe the system your app is running on. Here come some examples with inline comments:

//returns true on my PC as it is a 64-bit OS
bool is64BitOperatingSystem = Environment.Is64BitOperatingSystem;
//returns the machine name, in my case ANDRAS1
string machineName = Environment.MachineName;
			
//returns information about the operating system version, build, major, minor etc.
OperatingSystem os = Environment.OSVersion;
//returns the platform id as an enumeration, in my case it's Win32NT
PlatformID platform = os.Platform;			
//the currently installed service pack, Service Pack 1 in my case
string servicePack = os.ServicePack;
//the toString version of the OS, this is "Microsoft Windows NT 6.1.7601 Service Pack 1" on this PC
string version = os.VersionString;

//I have 4 processors on this PC
int processorCount = Environment.ProcessorCount;

//returns 2 logical drives: C: and D:
string[] logicalDrives = Environment.GetLogicalDrives();

//this is how to find all environmental variables of the system and iterate through them
IDictionary envVars = Environment.GetEnvironmentVariables();
foreach (string key in envVars.Keys)
{
	//e.g. the JAVA_HOME env.var is set to "C:\Progra~1\Java\jdk1.7.0_51\"
	Debug.WriteLine(string.Concat("key: ", key, ": ", envVars[key]));
}

//retrieve the current CLR version, in my case it's "4.0.30319.18444"
Version clrVersion = Environment.Version;

View all posts related to diagnostics here.

Filed under .NET, Diagnostics Tagged with ,

Using Amazon Elastic MapReduce with the AWS.NET API Part 1: introduction

February 16, 2015 Leave a comment

Introduction

Big Data is everywhere nowadays. It’s one of the most (over)used keywords in IT nowadays. Organisations have to process large amounts of information in form of messages in real time in order to make decisions about the future of the company. Companies can also use these messages as data points of something they monitor constantly: sales, response times, stock prices, etc. Their goal is presumably to process the data and extract information from it that they themselves or their customers find useful and are willing to pay for.

Amazon Web Services have a solution for pretty much anything in IT so it’s no surprise that there are at least two solutions for data mining and analysis scenarios:

Read more of this post

Filed under .NET, Amazon, Big Data Tagged with , , , , , ,

Replacing a value in a Map in Java 8

February 15, 2015 Leave a comment

The Java 8 SDK has a couple of interesting new default “replace” methods available on the Map interface.

Consider the following HashMap:

Map<String, String> sizes = new HashMap<>();
sizes.put("XS", "Extra small");
sizes.put("S", "Small");
sizes.put("M", "Medium");
sizes.put("L", "Large");
sizes.put("XL", "Extra large");
sizes.put("XXL", "Extra extra large");

Say we’d like to replace the value of key “S”:

String replacedValue = sizes.replace("S", "Small size");

The replace method returns the value of the replaced string. In the above case the key “S” will have a new value “Small size” and “replace” returns “Small” as it was the value of “S” before the replace operation.

Read more of this post

Filed under Java Tagged with , ,

Conditionally remove elements from a List in Java 8

February 14, 2015 8 Comments

Java 8 introduces a new method available for Collection types: removeif(). It accepts a predicate which defines the condition on which the elements should be removed. It returns a boolean where a true response means that at least one item has been removed and false otherwise:

Collection<String> stringStack = new Stack<>();
stringStack.add("Hello");
stringStack.add("my");
stringStack.add("dear");
stringStack.add("world");
        
stringStack.removeIf(s -> s.contains("ll"));

The above example will remove “Hello” from the list stack.

Note that not all collections support item removal. In that case the method will throw an UnsupportedOperationException in case an attempt is made to remove a matching element. The ArrayList is one such collection:

Collection<String> asList = Arrays.asList("hello", "my", "dear", "world");
asList.removeIf(s -> s.contains("ll"));

This will throw an exception unfortunately as the Array.asList method returns an ArrayList of type java.util.Arrays.ArrayList (which is read only and fixed size) and not the classic java.util.ArrayList (resizable and item-removable) – based on a comment by Juanito below.

View all posts related to Java here.

Filed under Java Tagged with , ,

Resolving null values in C#

February 13, 2015 Leave a comment

Say you have a method which accepts a string parameter. The method may need to handle null values in some way. One strategy is to validate the parameter and throw an exception:

private static string Resolve(string input)
{
	if (input == null) throw new ArgumentNullException("Input");
.
.
.
}

Another strategy is to provide some default value with an if-else statement:

Read more of this post

Filed under .NET, C# language features Tagged with ,

Using Amazon DynamoDb with the AWS .NET API Part 7: its place in Big Data

February 12, 2015 6 Comments

Introduction

In the previous post we looked at how to query our test table in Amazon DynamoDb. That post also completed our main discussion on how to use DynamoDb in .NET.

This post is dedicated to a larger picture: Big Data. This series is part of a large series on cloud-based Big Data infrastructure along with the message handler Amazon Kinesis and the raw data storage S3. Therefore the pre-requisite of following the discussion in this post is familiarity with what we discussed in those posts or at least some knowledge of Big Data. However, I’ll try to write in a way that those of you who’ve only come here for DynamoDb may get a taste of the role it can play in a cloud-based Big Data architecture.

Read more of this post

Filed under .NET, Amazon, Big Data Tagged with , , , , ,

← Older posts

Newer posts →

Elliot Balynn's Blog

A directory of wonderful thoughts

Software Engineering

Web development

Disparate Opinions

Various tidbits

chsakell's Blog

WEB APPLICATION DEVELOPMENT TUTORIALS WITH OPEN-SOURCE PROJECTS

Once Upon a Camayoc

ARCHIVED: Bite-size insight on Cyber Security for the not too technical.