Extending base class containing abstract generic method in java -

Extending base class containing abstract generic method in java -

i given base of operations class this:

class mybase{ public abstract <t> pupil assign (t object); }

i extending below:

class myclass extends mybase{ @override public abstract <t> pupil assign (t object){ pupil stew = new student(); ...... } }

my intended utilize is: passed in object should of type teacher. within method want create new pupil values invoking functions on teacher. (for example, stew.setteachername = teacher.getname();) , homecoming pupil caller.

questions: a) how intended behavior? b) whats difference between declaring mybase current way vs. doing mybase ? c) interested in knowing solution in case can alter base of operations class , cannot alter base of operations class.

thanks in advance help. also, if there useful resources/tutorials can point me great. again.

if cannot modify base of operations class, there isn't way involves generics. there 2 things do. one, check run-time type of object , 1 thing if teacher, if not.

public class myclass extends mybase { @override public <t> pupil assign(t object) { pupil student = new student(); if (object instanceof teacher) { teacher teacher = (teacher) object; student.setteachername(teacher.getname()); } else { student.setteachername("unknown"); } homecoming student; } }

two, create 2 separate assign methods in myclass, 1 overrides generic method in base of operations class, , non-generic method takes teacher parameter.

public class myclass extends mybase { @override public <t> pupil assign(t object) { homecoming new student(); } public pupil assign(teacher teacher) { pupil student = new student(); student.setteachername(teacher.getname()); homecoming student; } }

when method called, if compile-time type teacher, compiler take more specific overload of method:

public class main { /** * gets teacher calls object. * * @return object happens teacher */ public static object getteacher() { homecoming new teacher(); } public static void main(string[] args) { /** teacher, , declared such */ teacher teacher = new teacher(); /** * object, happens * teacher (but compiler can't see that) */ object = getteacher(); myclass mc = new myclass(); pupil withteacher = mc.assign(teacher); pupil withoutteacher = mc.assign(something); } }

however, much prefer 1 of solutions modifies mybase.

edited add: declare second, more specific assign method generic method, so:

public <t extends teacher> pupil assign(t object) { pupil student = new student(); student.setteachername(object.getname()); homecoming student; }

but same sec illustration above. method not override method in base of operations class, still relies on compiler picking more specific overload @ compile time, , erasure of method signature same non-generic method in sec example:

public pupil assign(teacher)

it looks bit more override of method base of operations class because it's got generic type variable , parameter named object instead of teacher. seek sticking @override annotation on , compiler tell not override or implement method supertype.

and still have <t> generic method hanging around doesn't set teacher name, , if ever have teacher object not declared such, compiler take wrong overload , you'll scratching head wondering why, if object teacher, teacher name didn't set on student.

java generics java-7 abstract