Command Line Arguments

Java provides an option like, a java application can accept any number of arguments from command line. This option facilitates us to configure Application at the time of running.

User should pass command line arguments, at the time of launching application.

Syntax

   java ClassName arguments

When an application launched, The command line arguments are copied to the String argument of the main method.

Example 1

class CommandLine{
  public static void main(String args[]){
    System.out.println("Number of arguments passes is " + args.length);
  
    for(int i=0; i < args.length; i++){
      System.out.println(args[i]);
    }
  }
}

Run the Application like below

   java CommandLine Hi How Are You

Output

Number of arguments passes is 4
Hi
How
Are
You

As you see args[0] contains String “Hi” args[1] contains “How” etc.,

Example 2

class CommandLine{
  public static void main(String args[]){
    if(args[0].equals("Day"))
      System.out.println("Good Morning, Have a Great Day");

    if(args[0].equals("Night"))
      System.out.println("Sleep Well, Good Night");
  }
}

Run 1

java CommandLine Day

Good Morning, Have a Great Day

Run 2

java CommandLine Night

Sleep Well, Good Night

Some Points to Remember

1. If no command line arguments are provided then, length of args is zero

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

 

Output
0    

        

2. If there is no command line arguments, then the String array of Main method will be empty or null?

It is Empty,not null.

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