The first Java program

import java.lang.*;

public class First {
  public static void main(String[] args) {
    System.out.println("This is my first Java program.");
  }
}

The statements have the following meaning:

• import java.lang.*; request to use libraries of predefined classes/programs (in fact, the java.lang library is imported automatically, hence this statement can be omitted)
• public class First {...} definition of a class/program called First
• public static void main(String[] args) {...} definition of the main method (a method is the realization of an operation in Java)
• System.out.println("This is my first Java program."); statement to print a message on the video
• System.out predefined object/instance of the predefined class PrintStream
• println method of the class PrintStream applied to the object System.out
• "This is my first Java program." object of the class String representing the sentence to display

Note: Java is case-sensitive, i.e., there is a difference between lower-case and upper-case letters. E.g., class is different from Class.