Keyword final

In Java, keyword final has three functions, as follows:

• When used to declare a variable, then the value of the variable can not be changed.
• When used to declare a method, then the method can not be overridden by derived class.
• When used to define a class, then the class can no longer be derived to new class.

Here, the point which we will discuss only the first point only. Second and third points will be discussed later in next post, when we talk about inheritance to a derived class.

If we want to use keyword final to declare a variable as a constant, then we need to fill the value into the variable. The value will be fixed or can not be changed during the execution of the program. Here is the general form of the declaration of a constant in Java:

access-modifier final data-type constant-name = value;

Just as in C/C ++, in Java, constants are generally written in capital letters. Here are some examples of declaring constants:

final double PI = 3.1416;
private final int ERROR = -1;
private final int ENGLISH = 1;
private final int ARABIC = 0;
private final String FILE_MENU_TITLE = "File";
private final String EXIT_BUTTON_TITLE = "Exit";