How to check if a subclass is an instance of a class at runtime

Question

In an android app test suite I have a class like this where B is a view   public class A extends B       etc        now I have a list of view objects which may contain A objects but in this case I only care if they re subclasses or  instances of  B  I d like to do something like   ArrayList lt View gt  viewList   getViews    Iterator lt View gt  iterator   viewList iterator    while  iterator hasNext    amp  amp  viewList    null        View view   iterator next        if  view getClass   isInstance B class                this is an instance of B           The problem is that when the if encounters an A object it doesn t evaluate to an  instance of B   Is there a way to do isSubclassOf or something

User · Accepted Answer

You have to read the API carefully for this methods. Sometimes you can get confused very easily.

It is either:

if (B.class.isInstance(view))

API says: Determines if the specified Object (the parameter) is assignment-compatible with the object represented by this Class (The class object you are calling the method at)

or:

if (B.class.isAssignableFrom(view.getClass()))

API says: Determines if the class or interface represented by this Class object is either the same as, or is a superclass or superinterface of, the class or interface represented by the specified Class parameter

or (without reflection and the recommended one):

if (view instanceof B)

User · Answer

If there is polymorphism such as checking SQLRecoverableException vs SQLException  it can be done like that   try          sth may throw exception            catch  Exception e        if SQLException class isAssignableFrom e getCause   getClass                      do sth         System out println  SQLException occurs               Simply say    ChildClass child  new ChildClass    if ParentClass class isAssignableFrom child getClass              do sth

User · Answer

if view instanceof B    This will return true if view is an instance of B or the subclass A  or any subclass of B for that matter

User · Answer

I ve never actually used this  but try view getClass   getGenericSuperclass

User · Answer

Class isAssignableFrom   - works for interfaces as well  If you don t want that  you ll have to call getSuperclass   and test until you reach Object

User · Answer

It s the other way around  B class isInstance view

User · Answer

Maybe I m missing something  but wouldn t this suffice   if  view instanceof B           this view is an instance of B

[java] How to check if a subclass is an instance of a class at runtime?

Examples related to java

Examples related to subclass

Examples related to instanceof