How to test if one java class extends another at runtime?
98,246
Solution 1
Are you looking for:
Super.class.isAssignableFrom(Sub.class)
Solution 2
If you want to know whether or not a Class
extends another, use Class#isAssignableFrom(Class). For your example, it would be:
if(B.class.isAssignableFrom(A.class)) { ... }
If you're interested in whether or not an instance is of a particular type, use instanceof
:
A obj = new A();
if(obj instanceof B) { ... }
Note that these will return true
if the class/instance is a member of the type hierarchy and are not restrictive to direct superclass/subclass relationships. For example:
// if A.class extends B.class, and B.class extends C.class
C.class.isAssignableFrom(A.class); // evaluates to true
// ...and...
new A() instanceof C; // evaluates to true
If you want to check for direct superclass/subclass relationships, Tim has provided an answer as well.
Solution 3
You want to know if b
is assignable from a
:
b.isAssignableFrom(a);
Additionally, if you want to know that a
is a direct subclass of b
:
a.getSuperclass().equals(b);
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Author by
Armand
Updated on September 15, 2020Comments
-
Armand almost 4 years
How to I test if
a
is a subclass ofb
?Class<?> a = A.class; Class<?> b = B.class;
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meriton almost 14 yearsActually, it B.class.isAssignableFrom(A.class), since he wants to know if A is a subclass of B.
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Rob Hruska almost 14 yearsAh yes, I'll change that. Usually examples are the other way around (B extending A).
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Armand almost 14 yearstricked ya ;-p Many thanks for the detailed answer; I'm accepting meriton's though, as it is the clearest IMO.
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Armand almost 14 yearsthanks for the answer, and thanks for using
a
andb
from the question