Java Object-oriented programming (IX)--final

1. Final concept

Final can modify variables or methods. In some cases, the programmer may have the following requirements:

A, when you do not want a method of the parent class to overwrite (override) The quilt class, you can use the final keyword to decorate.

b, when you do not want the value of a variable of a class to be modified, you can use the final decoration. If a variable is final, the initial value must be assigned, or a compilation error occurs.

C, when you do not want the class to be inherited, you can use the final decoration .

//use of the final method [Demo128.java] Public classDemo128 { Public Static voidMain (string[] args) {AAA AAA=NewAaa ();        Aaa.show (); BBB BBB=NewBBB ();    Bbb.show (); }}classaaa{inta=0;//If a does not assign an initial value, a is 0. Value should be assigned after defining the type//PI does not allow modification//a variable with a final decoration should be named with an underscore to differentiate the representation. This is the standard for Java programmers.     Final floatreate_1=3.1415926f;//use final to ensure that data that needs to be forced to be unmodified must be locked with final//final int b; //when you use final to define a variable, you must assign an initial value or an error. //b=1;    Final  Public voidSendmes () {//using final to modify a member method means that it cannot be modified and cannot be overwritten. SYSTEM.OUT.PRINTLN ("Send Message"); }     Public voidShow () {System.out.println ("A=" +a); }}Final classBbbextendsaaa{//defining a class before and final means that the class is not allowed to be inherited     PublicBbb () {a++; //reate_1=reate+1;    }    /*Public void Sendmes () {System.out.println ("Send Message")}*/}

final-- Precautions

1. The final modified variable is also called constant, which is usually named by Xx_xx_xx. (underlined)

2. When the final modified variable is defined, it must be assigned and cannot be assigned later.

final-- when do you use

1, because of case considerations, a method of the class does not allow modification.

2. Classes are not inherited by other classes.

3, some variable values are fixed, such as Pi 3.1415926