Java - Basic Syntax

When we consider a Java program, it can be defined as a collection of objects that communicate via invoking each other's methods. Let us now briefly look into what do class, object, methods, and instance variables mean.

·        Object − Objects have states and behaviors. Example: A dog has states - color, name, breed as well as behavior such as wagging their tail, barking, eating. An object is an instance of a class.

·        Class − A class can be defined as a template/blueprint that describes the behavior/state that the object of its type supports.

·        Methods − A method is basically a behavior. A class can contain many methods. It is in methods where the logics are written, data is manipulated and all the actions are executed.

·        Instance Variables − Each object has its unique set of instance variables. An object's state is created by the values assigned to these instance variables.

public class MyFirstJavaProgram {

   /* This is my first java program.

    * This will print 'Hello World' as the output

    */

   public static void main(String []args) {

      System.out.println("Hello World"); // prints Hello World

   }

}

Let's look at how to save the file, compile, and run the program. Please follow the subsequent steps −

·        Open notepad and add the code as above.

·        Save the file as: MyFirstJavaProgram.java.

·        Open a command prompt window and go to the directory where you saved the class. Assume it's C:\.

·        Type 'javac MyFirstJavaProgram.java' and press enter to compile your code. If there are no errors in your code, the command prompt will take you to the next line (Assumption : The path variable is set).

·        Now, type ' java MyFirstJavaProgram ' to run your program.

·        You will be able to see ' Hello World ' printed on the window