finalkeywordinjava abstract,interface,implementation.-170702034453.ppt

about keyword

1. Final Keyword In Java

2. •Thefinalkeywordinjavaisusedtorestrict
theuser.Thejavafinalkeywordcanbeusedin
manycontext.Finalcanbe:
•variable
•method
•class

3. •Thefinalkeywordcanbeappliedwiththe
variables,afinalvariablethathavenovalueit
iscalledblankfinalvariableoruninitialized
finalvariable.Itcanbeinitializedinthe
constructoronly.Theblankfinalvariablecan
bestaticalsowhichwillbeinitializedinthe
staticblockonly.
•Let'sfirstlearnthebasicsoffinalkeyword.

4. Java final variable
•Ifyoumakeanyvariableasfinal,youcannot
changethevalueoffinalvariable(Itwillbe
constant).

5. Example of final variable
•Thereisafinalvariablespeedlimit,weare
goingtochangethevalueofthisvariable,but
Itcan'tbechangedbecausefinalvariableonce
assignedavaluecanneverbechanged.

6. •classBike9{
•finalintspeedlimit=90;//finalvariable
•voidrun(){
•speedlimit=400;
•}
•publicstaticvoidmain(Stringargs[]){
•Bike9obj=newBike9();
•obj.run();
•}
•}//endofclass

7. Java final method
•If you make any method as final, you cannot
override it.

8. classBike{
finalvoidrun(){System.out.println("running");
}}
classHondaextendsBike{
voidrun(){System.out.println("runningsafelywi
th100kmph");}
publicstaticvoidmain(Stringargs[]){
Hondahonda=newHonda();
honda.run();
}}

9. Java final class
•If you make any class as final, you cannot
extend it.

10. finalclassBike{}
classHonda1extendsBike
{
voidrun()
{System.out.println("runningsafelywith100kmph")
;
}
publicstaticvoidmain(Stringargs[]){
Honda1honda=newHonda();
honda.run();
}
}

11. Is final method inherited?
•Yes, final method is inherited but you cannot
override it.

12. •classBike
•{
•finalvoidrun(){System.out.println("running..
.");}
•}
•classHonda2extendsBike{
•publicstaticvoidmain(Stringargs[]){
•newHonda2().run();
•}
•}

13. What is blank or uninitialized final
variable?
•Afinalvariablethatisnotinitializedatthe
timeofdeclarationisknownasblankfinal
variable.
•Ifyouwanttocreateavariablethatis
initializedatthetimeofcreatingobjectand
onceinitializedmaynotbechanged,itis
useful.ForexamplePANCARDnumberofan
employee.
•Itcanbeinitializedonlyinconstructor.

14. Can we initialize blank final variable?
•Yes, but only in constructor.

15. •classBike10{
•finalintspeedlimit;//blankfinalvariable
•
•Bike10(){
•speedlimit=70;
•System.out.println(speedlimit);
•}
•
•publicstaticvoidmain(Stringargs[]){
•newBike10();
•}
•}

16. static blank final variable
•Astaticfinalvariablethatisnotinitializedat
thetimeofdeclarationisknownasstatic
blankfinalvariable.Itcanbeinitializedonlyin
staticblock.

17. classA
{
staticfinalintdata;//staticblankfinalvariable
static
{
data=50;
}
publicstaticvoidmain(Stringargs[]){
System.out.println(A.data);
}
}

18. What is final parameter?
•Ifyoudeclareanyparameterasfinal,you
cannotchangethevalueofit.

19. •classBike11{
•intcube(finalintn)
•{
•n=n+2;//can'tbechangedasnisfinal
•n*n*n;
•}
•publicstaticvoidmain(Stringargs[]){
•Bike11b=newBike11();
•b.cube(5);
•}}

20. Can we declare a constructor final?
•No, because constructor is never inherited.