Java Hello World (Console)

This is a short tutorial for your first application in Java. I use Eclipse as software integrated developer environment (IDE), however there are many more (like Netbeans).

Let's start off with basic installation. First thing you need to install is Java Development Kit (JDK). After JDK, you need to install Eclipse IDE for Java Developers.

Open your Eclipse and click on "File"->"New"->"Project". Select "Java Project" and click "Next".

Type in a name like "HelloJava" and click "Finish".

A folder named HelloJava is created on left side of screen (Package Explorer). If you double click on that folder you can see its contents. Right-click on src subfolder and select "New"->"Package". Name it test.hello and click "Finish".

Now your package will appear in src subfolder. Right click on that package and select "New"->"Class". In name field type Hello and check the "public static void main(String[] args)" option. Click "Finish".

After this you will get some code that looks like this:

package test.hello;

public class Hello {

 /**
  * @param args
  */
 public static void main(String[] args) {
  // TODO Auto-generated method stub
 }
}

Now add a line System.out.println("This is my Hello Java!"); within main method so  it looks like following:

package test.hello;

public class Hello {

 /**
  * @param args
  */
 public static void main(String[] args) {
  // TODO Auto-generated method stub
  
  System.out.println("This is my Hello Java!");
 }
}

System.out.println("Something, something");  is used to print out whatever is contained within quotation marks (in this case it will print out Something, something.

To run the program, click on green "play" button in upper left corner or press CTRL+F11. Result of your program will appear below your code in console.

Now let's add text input. For this we need to create a Scanner. It will save whatever we write in one line and then we can use it to print out what has been saved in it. To do this we need to insert two lines above our current code. First line is the declaration of Scanner with name "scanner" and it should be Scanner scanner = new Scanner(System.in);. You will notice that the word Scanner is underlined. It means you need to import that class to your project. To do this, simply hover over the word Scanner and select "import java.util.Scanner;". Second line is for printing text and it should be System.out.println(scanner.nextLine()); Your code should now look like this:

package test.hello;

import java.util.Scanner;

public class Hello {
 /**
  * @param args
  */
 public static void main(String[] args) {
  // TODO Auto-generated method stub

  Scanner scanner = new Scanner(System.in);
  System.out.println(scanner.nextLine());
 }
}

Now you can run it, type whatever you wish in console and when you press "Enter" (new line), it will repeat what you wrote. That's it! 

C# Hello World (Graphic User Interface)

We are going to create a Hello World with GUI (Graphic User Interface) in C#. Like in previous post we start by creating new project.

Click on "File"->"New"->"Project" or shortcut "CTRL+SHIFT+N".

Again, we click on Visual C# on left side, but this time we need to select Windows Forms Application on the right side of screen. Under name type HelloWorldGUI and click OK button. It should look like this:

This creates new project and a screen with a window appears. On the left side there is also Toolbox which contains different elements that can be dragged and dropped on window. If you don't see toolbox on left side go to "View"->"Toolbox" and it will appear.

Select a Button from toolbox and drag and drop it on the window. Then select Label from toolbox and drag and drop it on the window under button. It should look like this:

Now click once on the window and take a look at lower right part of screen where it says Properties. Find where it says Text in list and write down My First GUI. This will change the text in upper left corner of your window from default text (which is usually Form1) to whatever you write in Text field.

Select button that is inside window, go to properties again, and under Text type Click me! in order to change text on the button.

Now select label that is inside window, go to properties again, and under Text type Button not clicked in order to change text on the label. Now go to (Name) property and change it to myLabel. This will set the name of label which we can use in our code. After renaming GUI should look like this:

Next step is double click on button. This will create a function for clicking on a button (click event). Here we get a code that looks something like this:

 using System;  
 using System.Collections.Generic;  
 using System.ComponentModel;  
 using System.Data;  
 using System.Drawing;  
 using System.Linq;  
 using System.Text;  
 using System.Windows.Forms;  
 namespace HelloWorldGUI  
 {  
   public partial class Form1 : Form  
   {  
     public Form1()  
     {  
       InitializeComponent();  
     }  
     private void button1_Click(object sender, EventArgs e)  
     {  
     }  
   }  
 }  

In order to change text on our label we add a line myLabel.Text = "Hello World!"; so that our code looks something like this:

 using System;  
 using System.Collections.Generic;  
 using System.ComponentModel;  
 using System.Data;  
 using System.Drawing;  
 using System.Linq;  
 using System.Text;  
 using System.Windows.Forms;  
 namespace HelloWorldGUI  
 {  
   public partial class Form1 : Form  
   {  
     public Form1()  
     {  
       InitializeComponent();  
     }  
     private void button1_Click(object sender, EventArgs e)  
     {  
       myLabel.Text = "Hello World!";  
     }  
   }  
 }  

Now run it by pressing F5 and try clicking the button.

Finally let's create a counter for our button that counts how many times it has been pressed. First we initialize an integer by putting int counter=0; before public Form1(). This creates a variable that has initial value 0. Inside our button click function - private void button1_Click we need to increase value of counter. This can be done by typing counter++; or counter = counter + 1; - either one will increase value of counter each time button is pressed. Now instead of "Hello World!" we put "Button has been clicked "+counter+" times!" - this will type out text "Button has been clicked" and "times!", but thanks to + sign it will also print out value of counter between those two parts.

Final code should look like this:

 using System;  
 using System.Collections.Generic;  
 using System.ComponentModel;  
 using System.Data;  
 using System.Drawing;  
 using System.Linq;  
 using System.Text;  
 using System.Windows.Forms;  
 namespace HelloWorldGUI  
 {  
   public partial class Form1 : Form  
   {  
     int counter = 0;  
     public Form1()  
     {  
       InitializeComponent();  
     }  
     private void button1_Click(object sender, EventArgs e)  
     {  
       counter++;  
       myLabel.Text = "Button has been clicked " + counter + " times";  
     }  
   }  
 }  

Try running it and keep clicking the button. Your results should look like this:

C# Hello World (Console)

This is a short tutorial for your first application in C#. Although there are many implementations of C# (like Mono), I will provide tutorial in Microsoft's Visual Studio.

First we will create "Hello World" console application. These are the steps:

Click on "File"->"New"->"Project" or shortcut "CTRL+SHIFT+N".

New window will appear. On left side you can see different languages. Select Visual C#. This will open a list of most common project types on the right side of the window. Select Console Application. Now we have to name it - type MyFirstApplication in name field. While you do this, solution name will change accordingly. If you want you can also change default location of your project. When you are done click "OK" button.

Again new window appears with your first class already generated. You will see some premade code that looks like this:

 using System;  
 using System.Collections.Generic;  
 using System.Linq;  
 using System.Text;  
 namespace MyFirstApplication  
 {  
   class Program  
   {  
     static void Main(string[] args)  
     {  
     }  
   }  
 }  

Now add a line Console.WriteLine("This is my Hello World!"); within Main method so  it looks like following:

 using System;  
 using System.Collections.Generic;  
 using System.Linq;  
 using System.Text;  
 namespace MyFirstApplication  
 {  
   class Program  
   {  
     static void Main(string[] args)  
     {  
       Console.WriteLine("This is my Hello World!");  
     }  
   }  
 }  

Console.WriteLine("bla bla bla"); is used to print out whatever is contained within quotation marks (in this case it will print out bla bla bla.

To start program click on green "play" button or press F5. This will run your program, however you will most likely not be able to see what it prints out because console closes too fast. To avoid that we will add another line of code that requires user to press enter before console closes. Add this line below the last one
Console.ReadLine(); so that code looks like this:

 using System;  
 using System.Collections.Generic;  
 using System.Linq;  
 using System.Text;  
 namespace MyFirstApplication  
 {  
   class Program  
   {  
     static void Main(string[] args)  
     {  
       Console.WriteLine("This is my Hello World!");  
       Console.ReadLine();  
     }  
   }  
 }  

Now try running it again (F5). This time you can see the printed text and console waits for you to press enter in order to finish running.

Now let's try to enter a line of text and print out the text we entered. For this we need to create a String. It will save whatever we write in one line and then we can use it to print out what has been saved in it. To do this we need to insert two lines above our current code. First line is the declaration of String with name "message" and it should be String message;. Second line is for storing text from whatever line you write on keyboard and it should be message = Console.ReadLine();. Your code should now look like this:

 using System;  
 using System.Collections.Generic;  
 using System.Linq;  
 using System.Text;  
 namespace MyFirstApplication  
 {  
   class Program  
   {  
     static void Main(string[] args)  
     {  
       String message;  
       message = Console.ReadLine();  
       Console.WriteLine("This is my Hello World!");  
       Console.ReadLine();  
     }  
   }  
 }  

If you try to run it it will first request from you a line of text (when you press enter it will finish taking text), but it will print out This is my Hello World!. In order to change that we need to make it print out our message. To do this we simply remove "This is my Hello World!" and write message inside parentheses. Now the code should look like this:

 using System;  
 using System.Collections.Generic;  
 using System.Linq;  
 using System.Text;  
 namespace MyFirstApplication  
 {  
   class Program  
   {  
     static void Main(string[] args)  
     {  
       String message;  
       message = Console.ReadLine();  
       Console.WriteLine(message);  
       Console.ReadLine();  
     }  
   }  
 }  

And that's it!