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Every Java application requires a class containing a method named main. This module provides information on the main method.

Revised: Mon Mar 28 11:21:22 CDT 2016

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This module is part of a collection of modules designed to help you learn to program computers.

Every Java application requires a class containing a method named main . This module provides information on the main method.

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  • Figure 1 . The method signature according to Niemeyer and Peck.
  • Figure 2 . The method signature according to Oracle.
  • Figure 3 . Allowable signatures for the main method.

The main method in Java

There must be a main method in the controlling class in every Java application.

The method signature

The Java literature frequently refers to the signature of a method, or the method signature .

Exploring Java by Patrick Niemeyer and Joshua Peck (O'Reilly) provides the definition of a method signature shown in Figure 1 .

Figure 1. The method signature according to Niemeyer and Peck .
"A method signature is a collection of information about the method, as in a C prototype or a forward function declaration in other languages. It includesthe method's name, type, and visibility, as well as its arguments and return type."


Apparently in this definition, the authors are referring to the type of the method as distinguishing between static and non-static. (Other literature refers to the type of a function or method as being the return typewhich according to the above definition is a separate part of the signature.)


Apparently also the use of the word visibility in the above definition refers to the use of public , private , etc.

According to Oracle...

Oracle's Java Tutorials , on the other hand, describe the method signature as in Figure 2 .

Figure 2. The method signature according to Oracle .
Definition: Two of the components of a method declaration comprise the method signature -- the method's name and the parameter types.

As you can see, the Oracle definition is more restrictive than the Niemeyer and Peck definition.

Bottom line on method signature

The method signature can probably be thought of as providing information about the programming interface to the method. In other words, it provides the information that you need to be able to call themethod in your program code.

Signature of main method

The controlling class of every Java application must contain a main method having one of the signatures shown in Figure 3 .

Figure 3 . Allowable signatures for the main method.
public static void main(String[] args)public static void main(String args[])

(I prefer the first signature in Figure 3 as being the most descriptive of an array of String references which is what is passed in as an argument.)

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