first program on java

 

first program on java

public class First

{

public static void main(String[] args)

{

System.out.println("Hello java");

}

}

letus expand this

1. public class First

            public: it is access  specifier which tells us it is public and can be used anywhere inside or outside the package.

            class: it is actually keyword and class must start with this keyword

            First: class name or simply an identifier which is used to name the class

            Note: cass name should start with Capitel Letter.

            note: program has only one public class rest all are just deault class

2. public static void main(String[] args)

                public: it is access  specifier which tells us it is public and can be used anywhere inside or outside the package.

                static: which is used to allocate memory at compile time and also it represents whole class not as simple object.

                void: return type and void means return type is nothing.

                main: it is simply class name

                string [] args: array of string type

        note: every program has just one main method other are just to shape the program and our execuition starts form main method.

3. System.out.println("Hello java")

                System: is just a class.it is decleared as final.

                out: is an instance of the System class and is of type PrintStream

                  Println or print : is actally a method of PrintStream Class which is used to print thing that we are in need.

                note: our class has as many as these types of print messeges.