<p>When writing a Java program, it is important to make it user-friendly and interactive. One way to achieve this is by using command line arguments. These are parameters that can be passed to a Java program when it is executed, allowing the user to customize the program's behavior. In this article, we will discuss how to parse command line arguments in Java.</p>
<h2>The Basics of Command Line Arguments</h2>
<p>Before we dive into parsing command line arguments, let's first understand what they are. Command line arguments are strings of text that are passed to a program when it is executed through the command line interface. They are separated by spaces and can be used to provide input or specify settings for the program.</p>
<p>For example, if we have a Java program called <code>Calculator</code> and we want to pass two numbers <code>10</code> and <code>5</code> as arguments, we would execute the program as follows:</p>
<code>java Calculator 10 5</code>
<p>In this case, <code>10</code> and <code>5</code> are the command line arguments that will be passed to the <code>main</code> method of our <code>Calculator</code> program.</p>
<h2>Retrieving Command Line Arguments in Java</h2>
<p>Now that we know what command line arguments are, let's see how we can retrieve them in our Java program. The <code>main</code> method in Java has a parameter called <code>args</code> which is an array of strings. This array contains all the command line arguments that were passed when the program was executed.</p>
<p>We can access individual arguments by specifying their index in the array. For example, <code>args[0]</code> would give us the first argument, <code>args[1]</code> would give us the second argument, and so on. We can also use the <code>length</code> property of the <code>args</code> array to determine how many arguments were passed.</p>
<p>Let's modify our <code>Calculator</code> program to print out the two numbers that were passed as arguments:</p>
<pre><code>public class Calculator {
public static void main(String[] args) {
int num1 = Integer.parseInt(args[0]);
int num2 = Integer.parseInt(args[1]);
System.out.println("First number: " + num1);
System.out.println("Second number: " + num2);
}
}
</code></pre>
<p>If we execute this program with the same command line arguments as before, we will get the following output:</p>
<code>First number: 10
Second number: 5</code>
<p>As you can see, we have successfully retrieved the command line arguments and used them in our program.</p>
<h2>Parsing Command Line Arguments</h2>
<p>Now, let's say we want to make our <code>Calculator</code> program more robust by allowing the user to specify the operation to perform on the two numbers as a command line argument. For example, if the user wants to add the two numbers, they would execute the program as follows:</p>
