Command Line Argument In Java


In this article, we discuss command line arguments in Java.

What is command line argument

An argument passed when a Java program is run is called a command line argument. The arguments can be used as input. So, it provides a convenient way to check out the behavior of the program on various values. We can pass any number of arguments from the command prompt or nearly anywhere a Java program is executed. This allows the user to specify configuration information when the application is launched.
  • We can provide any number of arguments using a command line argument.
  • Information is passed as Strings. So we can convert it to numeric or another format easily.
  • While launching our application it is useful for configuration information.
1. Example
In this example, we are printing the first command line argument as in the following.
  1. class CommandLineEx {  
  2.     public static void main(String x[]) {  
  3.         System.out.println("First Command line Argument is: " + x[0]);  
  4.     }  
  5. }  
2. Example
In this example, we are printing or showing all the command-line arguments using a for loop.
  1. class CommandLineEx1 {  
  2.     public static void main(String x[]) {  
  3.         for (int a = 0; a < x.length; a++)  
  4.             System.out.println(x[a]);  
  5.     }  
  6. }  
3. Example
In this example; we show a program that supports only numeric command-line arguments, using parse int to convert a string value to a number (like "1234" string as a number 1234).
  1. class CommandLineEx2 {  
  2.     public static void main(String x[]) {  
  3.         int argFirst;  
  4.         if (x.length > 0) {  
  5.             try {  
  6.                 argFirst = Integer.parseInt(x[0]);  
  7.                 System.out.println(x[0]);  
  8.             } catch (NumberFormatException nfe) {  
  9.                 System.err.println("Given argument" + " should be an integer");  
  10.             }  
  11.         }  
  12.     }  
  13. }  
This program throws a NuberFormatException if the format of x[0] is not valid as in the following.
When we provide an integer value it works fine as in the following.