java - Interface-Class-Object,Casting,Exception -



java - Interface-Class-Object,Casting,Exception -

i saw code:

interface i{} class implements i{} class b extends a{} class c extends b{} class abc { public static void main(string args[]) { a=new a(); b b=new b(); a=(b)(i)b; //line 1 b=(b)(i)a; //line 2 a=(i)b; //line 3 i=(c)a; //line 4 } }

trying find out

which way have safe casting i.e without compile time or run time error in circumstances casting show compile time error in circumstances casting show run time exception

can 1 explain me these 3 concepts?

in java, interface similar class type. in illustration , object of class oftype , oftype i. object of class b oftype b, oftype(subtype) , oftype i. object of class c oftype c, oftype(subtype) b, oftype(subtype) , oftype i. noticed, objects oftypes of 2 types (te 2 types have no link each other i.e. , independently types) , subtypes of respective super classes.

as per leskov's substitution principal, can sunstiture subtype (sub-class) in place of supertype(super-class). illustrate @ code fragment below:

public class inheritancetest {

public interface i{} public class implements i{} public class b extends a{} public class c extends b{} public class d implements i{} public class e{} public void method(){ a=new a(); b b=new b(); c c=new c(); d d=new d(); i=null; i=a;i=b;i=c; a=b; b=c; a=c; a=(a)i;//a=i not work, , 2 different types i=d; a=(a)i;//classcastexception @ runtime, d not e e=new e(); //a=(a)e; - generates compile time error }//method closing

}//class closing

the cast necessary because, per code, all not i.e. have class d implemented unconnected inheritance hierarchy. in general, when have convert between 2 unconnected types, need cast.

note: have edited code include class d note: have edited code include class e

java object interface casting

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