2.17 Jb0180: java oop: the main method.  (Page 2/2)

public

The keyword public indicates that the method can be called by any object. A future module will discuss the keywords public , private , and protected in more detail.

static

The keyword static indicates that the method is a class method, which can be called without the requirement to instantiate an object ofthe class. This is used by the JVM to launch the program by calling the main method of the class identified in the command to start the program.

void

The keyword void indicates that the method doesn't return any value.

args

The formal parameter args is a reference to an array object of type String . The array elements contain references to String objects that encapsulate String representations of the arguments, if any, entered at thecommand line.

Note that the args parameter must be specified whether or not the user is required to enter command-line arguments and whetheror not the code in the program actually makes use of the argument. Also note that the name can be any legal Java identifier. It doesn't have to be args . It could be joe or sue, for example.

The length property

The parameter named args is a reference to an array object. Java array objects have a property named length , which specifies the number of elements in the array.

The runtime system monitors for the entry of command-line arguments by the user and constructs the String array containing those arguments.

Processing command-line arguments

The args.length property can be used by the code in the program to determine the number of arguments actually entered by the user.

If the length property is not equal to zero, the first string in the array corresponds to the first argument entered on the commandline.

Command-line arguments along with strings and String arrays will be discussed in more detail in a future module.

Miscellaneous

This section contains a variety of miscellaneous information.

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