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JavaRanch » Java Forums » Certification » Programmer Certification (SCJP/OCPJP)
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Generics

Suguna Gollapally
Ranch Hand

Joined: Oct 31, 2006
Posts: 37
import java.util.*;
class shape { }
class Rect extends shape { }
class cir extends shape { }
class shade extends Rect{}
class Test {

public static void add(List<? extends shape>l,int pos,Rect r) {

l.add(pos,r);
}

public static void main(String ar[]) {

List<shade>=new ArrayList<shade>();
add(l,o,newshade());
}
}
What is the error in this program?? is this add() method..
Keith Lynn
Ranch Hand

Joined: Feb 07, 2005
Posts: 2367
Originally posted by Suguna Gollapally:
import java.util.*;
class shape { }
class Rect extends shape { }
class cir extends shape { }
class shade extends Rect{}
class Test {

public static void add(List<? extends shape>l,int pos,Rect r) {

l.add(pos,r);
}

public static void main(String ar[]) {

List<shade>=new ArrayList<shade>();
add(l,o,newshade());
}
}
What is the error in this program?? is this add() method..


Because the parameter to the method accepts a List containing shape or anything that extends shape, there is no way to allow anything to be added to the List in the method.
 
It is sorta covered in the JavaRanch Style Guide.
 
subject: Generics
 
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