In Java, command line arguments are input parameters that are passed to the main method of a Java program when it is run. These arguments allow users to provide additional input to the program without having to modify the code.

Command line arguments are passed as strings and can be accessed from within the main method using the args parameter, which is an array of strings. The args array contains all the command line arguments that were passed to the program, with the first argument at index 0, the second argument at index 1, and so on.

Here is an example of a Java program that accepts command line arguments:

public class MyProgram {
    public static void main(String[] args) {
        System.out.println("Number of command line arguments: " + args.length);
        
        for (int i = 0; i < args.length; i++) {
            System.out.println("Argument " + i + ": " + args[i]);
        }
    }
}

In this example, the main method prints the number of command line arguments that were passed to the program, and then prints each argument to the console.

To run this program with command line arguments, you can use the java command followed by the name of the program and the arguments you want to pass, like this:

java MyProgram arg1 arg2 arg3

In this example, the program MyProgram is run with three command line arguments: arg1, arg2, and arg3. When the program runs, it will print the number of arguments and each argument to the console.

Note that command line arguments are always passed as strings, so if you need to use them as numbers or other data types, you will need to convert them using methods like Integer.parseInt() or Double.parseDouble().