|Lesson 5||Customizing applications with command-line arguments|
|Objective||Pass information to Java applications with command-line arguments.|
Pass information to Java applications with command-line arguments
Customizing Applications with command-line Arguments
In the previous lesson that the
method has some additional information listed after the method name.
This information is actually an application customization feature known as command-line arguments
Command-line arguments provide custom information to an application. They are entered on the command-line when an application is executed using the Java interpreter. Following is an example of passing a command-line argument to an application named LifeCalc that calculates the number of days, hours, and minutes that you have lived:
java LifeCalc 28
As you can see, the single command-line argument is entered on the command-line just after the application name. Following are the results of this command:
You have lived 10220 days.
Or you can think of it as 245280 hours.
Better still, how about 14716800 minutes.
Handling command-line arguments
The key to command-line arguments can be found in the main() method
public static void main(String args)
inside the parentheses is a method parameter, which is information passed into a method that the method might need to
know about. In this case, the
parameter contains the list of command-line arguments entered by the user at the command-line.
The argument list is stored as an array of strings
, which is basically a list of text. You learn about both arrays and strings in the next module, but for now just think of the
parameter as a container that holds the arguments passed into an application on the command-line. You can access each command-line argument individually.
You can determine the length of an array from its
length data member. For example, the number of command-line arguments is determined by the following data member:
The main method
is a method within a Java application that is called by the Java interpreter to run the application.