Using Command-Line Arguments

Using Command-Line Arguments

Sometimes you will want to pass information into a program when you run it. This is accomplished by passing command-line arguments to main( ). A command-line argument is the information that directly follows the program’s name on the command line when it is executed. To access the command-line arguments inside a Java program is quite easy—they are stored as strings in a String array passed to the args parameter of main( ). The first command-line argument is stored at args[0], the second at args[1], and so on. For example, the following program displays all of the command-line arguments that it is called with:

// Display all command-line arguments. 

class CommandLine {

public static void main(String args[]) { 

for(int i=0; i<args.length; i++)

System.out.println("args[" + i + "]: " + args[i]);

}

}

Try executing this program, as shown here:

java CommandLine this is a test 100 -1

When you do, you will see the following output:

args[0]: this 

args[1]: is 

args[2]: a 

args[3]: test 

args[4]: 100 

args[5]: -1