Command Line Argument In Java

Introduction

 

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.

 

Advantages

• 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.

 

CommandLineEx.java

class CommandLineEx {
    public static void main(String x[]) {
        System.out.println("First Command line Argument is: " + x[0]);
    }
}

Output

 

 

2. Example

 

In this example, we are printing or showing all the command-line arguments using a for loop.

 

CommandLineEx1.java

class CommandLineEx1 {
    public static void main(String x[]) {
        for (int a = 0; a < x.length; a++)
            System.out.println(x[a]);
    }
}

Output

 

 

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).

 

CommandLineEx2.java

class CommandLineEx2 {
    public static void main(String x[]) {
        int argFirst;
        if (x.length > 0) {
            try {
                argFirst = Integer.parseInt(x[0]);
                System.out.println(x[0]);
            } catch (NumberFormatException nfe) {
                System.err.println("Given argument" + " should be an integer");
            }
        }
    }
}

Output

 

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.