Slide 4.1: My first Java program

My First Java Program

Java is a high-level, object-oriented, class-based, concurrent, and general-purpose computer programming language. Java has a runtime environment (JRE) and API (together they are called a platform, which is any hardware or software environment in which a program runs). Below is a Java example which prints the text such as “Hello World” entered by users to the standard output:

MyFirstClass.java (a hello-world program)

 public class MyFirstClass {
   public static void main( String args[ ] ) {
     System.out.println( "" );
   }
 }

public keyword is an access modifier which represents visibility. It means it is visible to all.
class keyword is used to declare a class in Java.
static is a keyword. The core advantage of the static method is that there is no need to create an object to invoke the static method. The main method is executed by the JVM, so it does not require to create an object to invoke the main method, and saves memory.
void is the return type of the method. It means it does not return any value.
main represents the starting point of the program.
String[] args is used for command-line arguments.
System.out.println() is used to print statement, where System is a class, out is the object of PrintStream class, println is the method of PrintStream class.