Dawid's Blog

How to convert ArrayList to array in Java?

I've been working quite a lot in Java. Although this is part of the university course, we actually have some QAs we need to satisfy, and so the quality of the code matters. Every now and again (more often than not actually), I came across painfully annoying constructs which make the code that much harder

StackOverflow Survey is here

If you haven't seen already, StackOverflow has released their annual survey. It offers a valuable insight into the minds of other programmers, so don't forget to check it out! http://meta.stackoverflow.com/questions/342400/take-the-developer-survey-2017

Creating a Sequence (or set) in Epsilon

In order to create a sequence (or set) of elements use the following:

var seq : Sequence = Sequence {"Hello","Hello"};

1	var seq : Sequence = Sequence {"Hello","Hello"};

Quick Software Estimator

A simple software estimator, so that you can give a vague number to your boss. The number is an effort Size Type Organic Semi-detached Embedded Effort (in person months)

The curious case of banner468

On one of my websites, I used a CSS class called "banner468". As the name suggests the original purpose of the class was to hold some ads. I used it for a different purpose. From one day to the next, the functionality contained within the banner468, disappeared. It got hidden. Originally, I thought, this had

Serializing Anonymous DataMemeber

I've been working win MVC Web API and encountered an annoying problem. It does not, by default serialise anonymous data members.

[DataMember]
public object text = new { status = "generated", div = "<table><tr><th>Code</th><th>Interpreation</th></tr></table>"};

1 2	[DataMember] public object text = new { status = "generated", div = "<table><tr><th>Code</th><th>Interpreation</th></tr></table>"};

When you try to serialise this kind of data you get this beautiful exception:

Type '<>f__AnonymousType3`2[System.String,System.String]' cannot be serialised. Consider marking it with the DataContractAttribute attribute, and marking all of its members you want to be serialized with the DataMemberAttribute attribute.  If the type is a collection, consider marking it with the CollectionDataContractAttribute.  See the Microsoft .NET Framework documentation for other supported types.

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Type '<>f__AnonymousType3`2[System.String,System.String]' cannot be serialised. Consider marking it with the DataContractAttribute attribute, and marking all of its members you want to be serialized with the DataMemberAttribute attribute. If the type is a collection, consider marking it with the CollectionDataContractAttribute. See the Microsoft .NET Framework documentation for other supported types.

Converting anonymous type to a string also caused exception. But there is also JavaScriptSerializer:

    var x = new { blah = "afd" };
    JavaScriptSerializer serializer = new JavaScriptSerializer();
    var serialized = serializer.Serialize(x);

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var x = new { blah = "afd" };

JavaScriptSerializer serializer = new JavaScriptSerializer();

var serialized = serializer.Serialize(x);

Now using getter,

One way object binding in JS

This is something I've been putting together this weekend. Due to the fact, that ASP.NET is quite reluctant to get an array of results from a request, I've devised an alternative way of sending data to the server via Web.API. There are already several large frameworks that handle data-binding like Knockout and AngularJS, but these

Useful Linear Trendline Class in C#

I've searched and searched trying to find a simple class to calculate a slope and intercept from a set of points. Here is the outcome, but I probably modify it to use LINQ rather then loops

    public class Trendline
    {
        /// <summary>
        /// Get's the line's best fit slope of the line
        /// </summary>
        public double Slope { get; private set; }

        /// <summary>
        /// Get's the Mia
        /// </summary>
        public double Offset { get; private set; }

        public double[] ValuesX { get; private set; } 

        public double[] ValuesY { get; private set; }

        private double sumY;

        private double sumX;

        private double sumXY;

        private double sumX2;

        private double n;

        public Trendline(double[] x, double[] y)
        {
            this.ValuesX = x;
            this.ValuesY = y;

            this.sumXY = this.calculateSumXsYsProduct(this.ValuesX, this.ValuesY);
            this.sumX = this.calculateSumXs(this.ValuesX);
            this.sumY = this.calculateSumYs(this.ValuesY);
            this.sumX2 = this.calculateSumXsSquare(this.ValuesX);
            this.n = this.ValuesX.Length;

            this.calculateSlope();
            this.calculateOffset();
        }

        public Trendline(double[] y)
        {
            //Assinging Y Values
            this.ValuesY = y;
            int length = y.Length;
            //Assinging X Values
            this.ValuesX = new double[length];
            for (int i = 0; i < length; i++)
            {
                this.ValuesX[i] = i;
            }


            this.sumXY = this.calculateSumXsYsProduct(this.ValuesX, this.ValuesY);
            this.sumX = this.calculateSumXs(this.ValuesX);
            this.sumY = this.calculateSumYs(this.ValuesY);
            this.sumX2 = this.calculateSumXsSquare(this.ValuesX);
            this.n = this.ValuesX.Length;
        }

        public Trendline(double[][] xy)
        {
            double[] xs = new double[xy.Length];
            double[] ys = new double[xy.Length];
            for (int i = 0; i < xy.Length; i++)
            {
                xs[i] = xy[i][0];
                ys[i] = xy[i][1];
            }
            this.ValuesX = xs;
            this.ValuesY = ys;
        }

        private double calculateSumXsYsProduct(double[] xs, double[] ys)
        {
            double sum = 0;
            for (int i = 0; i < xs.Length; i++)
            {
                sum += xs[i] * ys[i];
            }
            return sum;
        }

        private double calculateSumXs(double[] xs)
        {
            double sum = 0;
            foreach (double x in xs) {
                sum += x;
            }
            return sum;
        }

        private double calculateSumYs(double[] ys)
        {
            double sum = 0;
            foreach (double y in ys)
            {
                sum += y;
            }
            return sum;
        }

        private double calculateSumXsSquare(double[] xs)
        {
            double sum = 0;
            foreach (double x in xs)
            {
                sum += System.Math.Pow(x,2);
            }
            return sum;
        }

        private void calculateSlope()
        {
            try
            {
                Slope = (n * sumXY - sumX * sumY) / (n * sumX2 - System.Math.Pow(sumX,2));
            }
            catch (DivideByZeroException)
            {
                Slope = 0;
            }
        }

        private void calculateOffset()
        {
            try
            {
                Slope = (sumY - Slope * sumX) / n;
            }
            catch (DivideByZeroException) { }
        }
    }

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public class Trendline

{

/// <summary>

/// Get's the line's best fit slope of the line

/// </summary>

public double Slope { get; private set; }

/// <summary>

/// Get's the Mia

/// </summary>

public double Offset { get; private set; }

public double[] ValuesX { get; private set; }

public double[] ValuesY { get; private set; }

private double sumY;

private double sumX;

private double sumXY;

private double sumX2;

private double n;

public Trendline(double[] x, double[] y)

{

this.ValuesX = x;

this.ValuesY = y;

this.sumXY = this.calculateSumXsYsProduct(this.ValuesX, this.ValuesY);

this.sumX = this.calculateSumXs(this.ValuesX);

this.sumY = this.calculateSumYs(this.ValuesY);

this.sumX2 = this.calculateSumXsSquare(this.ValuesX);

this.n = this.ValuesX.Length;

this.calculateSlope();

this.calculateOffset();

}

public Trendline(double[] y)

{

//Assinging Y Values

this.ValuesY = y;

int length = y.Length;

//Assinging X Values

this.ValuesX = new double[length];

for (int i = 0; i < length; i++)

{

this.ValuesX[i] = i;

}

this.sumXY = this.calculateSumXsYsProduct(this.ValuesX, this.ValuesY);

this.sumX = this.calculateSumXs(this.ValuesX);

this.sumY = this.calculateSumYs(this.ValuesY);

this.sumX2 = this.calculateSumXsSquare(this.ValuesX);

this.n = this.ValuesX.Length;

}

public Trendline(double[][] xy)

{

double[] xs = new double[xy.Length];

double[] ys = new double[xy.Length];

for (int i = 0; i < xy.Length; i++)

{

xs[i] = xy[i][0];

ys[i] = xy[i][1];

}

this.ValuesX = xs;

this.ValuesY = ys;

}

private double calculateSumXsYsProduct(double[] xs, double[] ys)

{

double sum = 0;

for (int i = 0; i < xs.Length; i++)

{

sum += xs[i] * ys[i];

}

return sum;

}

private double calculateSumXs(double[] xs)

{

double sum = 0;

foreach (double x in xs) {

sum += x;

}

return sum;

}

private double calculateSumYs(double[] ys)

{

double sum = 0;

foreach (double y in ys)

{

sum += y;

}

return sum;

}

private double calculateSumXsSquare(double[] xs)

{

double sum = 0;

foreach (double x in xs)

{

sum += System.Math.Pow(x,2);

}

return sum;

}

private void calculateSlope()

{

try

{

Slope = (n * sumXY - sumX * sumY) / (n * sumX2 - System.Math.Pow(sumX,2));

}

catch (DivideByZeroException)

{

Slope = 0;

}

private void calculateOffset()

{

try

{

Slope = (sumY - Slope * sumX) / n;

}

catch (DivideByZeroException) { }

}

(Remote) File-Based Communication

Scenario: Applications C and P run on the same machines, but are implemented in different programming languages. P contains the functionality that can return a list of addresses given a postcode and C needs to reuse this functionality. If the pieces of code run on the same machines we could implement a file-based communication pattern. We

Introduction to Services

Large enterprises typically own and operate a large number of software applications either of the shelf, developed in-house or inherited through mergers and acquisitions. Applications can be of heterogeneous e.g. they are written in the same language(s) or they use the same data storage mechanisms and formats. They may also run on the same operating

The Blog

How to convert ArrayList to array in Java?

StackOverflow Survey is here

Creating a Sequence (or set) in Epsilon

Quick Software Estimator

The curious case of banner468

Serializing Anonymous DataMemeber

One way object binding in JS

Useful Linear Trendline Class in C#

(Remote) File-Based Communication

Introduction to Services

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