Command-Line Arguments

 

---

 

Overview

Java parses command-line arguments specified after the name of the class:

java Class arg1 arg2 arg3 ...

The runtime system passes the command-line arguments to the app's main method via an array of Strings called args.

1. To display command-line arguments:

   public class Echo 
   {
       public static void main (String[] args) 
       {
           for (int i = 0; i < args.length; i++)
               System.out.println(args[i]);
       }
   }
   
   
   $ java Echo Drink Hot Java
   Drink 
   Hot 
   Java
   

2. To display the output on a single line, enclose the arguments in double quotes:

   $ java Echo "Drink Hot Java"
   Drink Hot Java
   

3. To display the number of command-line arguments:

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

4. To parse numeric command-line arguments, convert String arguments to a number. For example, to convert an argument of "144" to an int:

   int firstArg;
   if (args.length > 0)
       firstArg = Integer.parseInt(args[0]);
   

   parseInt throws a NumberFormatException if the format of args[0] isn't valid.

 

---