First Java Application:
- The aim of first application is used to display “Hello world” message on output screen.
- The application as follows.
class Program
{
public static void main(String[] args)
{
System.out.println("Hello World!");
}
}
class:
- It is a keyword.
- It must be in lower case
- In Java, class represents object
- Every instruction belongs to class (we cannot write any code outside to class)
Class Name:
- In the above program, class name is “Program”.
- Application is a collection of programs.
- We can access the program using its name only.
main() method:
- Method is a block of instructions that performs a task.
- Java application execution starts from main() function.
- Main() is taking String array as argument(input)
- Arguments are called Signature of method.
Why main() taking String array as input?
- Main() method is taking command line arguments as input in the form String array.
- In C language also, main() function only takes input from command line.
Command line:
- Command prompt is CUI based Operating System.
- For example MS-DOS
- In Computer every program runs by OS.
