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Introduction to Java

Java

Java is one of the most popular programming languages of the 21th century. The object-oriented programming language was created by Oracle in 1995, and can be used for many different purposes. It might be the programming language that pushed the object-oriented style of programming the most, and is pretty infamous for its boilerplate-loaded way of printing hello world.

Java is often referred to as very slow, due to its compiler-interpreter model. Yet, this is not true anymore. Java is actually able to run code very fast and in some scenarios not much slower than C++ or C.

Hello World in Java​

public class Main {
    public static void main(String[] args) {
        System.out.println("Hello world!");
    }
}

You can execute it with running

javac Main.java && java Main

Other code examples​

A basic class in Java​

public class Main {
  int x = 5;

  public static void main(String[] args) {
    Main myObj = new Main();
    System.out.println(myObj.x);
  }
}

This example is taken from w3schools.

Getting started with Java​

To get started, you need to install the Java SE for your machine. You can download a version here.

Once installed successfully, open your terminal or CMD and run java. In case it prints a ton of text, Java is installed successfully on your machine.

Running Hello world​

Up next is creating and running your fist Java program. Create a file called Main.java. Paste the contents for the hello world program shown above into the file. Once saved, you can compile it with: javac Main.java.

Now, Java compiled the program to bytecode for the virtual machine of Java. The bytecode is in the file "Main.class" and is not human-readable. This VM can now run the program:

java Main.

There you go! You just created your first Java program.

Author's Notes​

I had to learn it for multiple courses in University and never really liked it. Especially not, because Java really forces object oriented programming onto the programmer. Yet, one must admit that Java is evolving and isn't too bad for beginners.

Sources​

As the source, the official documentation is used.