CODEWITHSUNDEEP
javagenerics
athena
athena

Reputation: 5709

Finding actual type parameters in Java

I have a class 

class ClassA<B extends ClassC>
{
................
}

In another class I have a list of objects of type A.

List<A<?>> cl = new ArrayList<A<?>>();
cl.add(new ClassB1(....));

where ClassB1 extends ClassC. How can I find out the type of objects in the list? i.e. The first object in the list is of type ClassB1.

Adding actual code 

ClassA<ClassB1> af = new ClassA<ClassB1>(); 
List<ClassA<?>> afl = new ArrayList<ClassA<?>>(); 
afl.add(af); 
for(ClassA<?> a: afl) 
    System.out.println(a.getClass());

This prints only ClassA and not ClassB1.

Upvotes: 0

Views: 142

Answers (2)

Bozho
Bozho

Reputation: 597076

If you put objects of different classes, you can iterate the list and use getClass().

Update: this information is lost at runtime due to type erasure. So you can't get it.

Upvotes: 2

corsiKa
corsiKa

Reputation: 82559

You can get the class with getClass() if you really, really, realllllyyy need to.

However, I would advise you to reconsider the notion of needing to get the class in the first place. If you're going to treat the classes differently, it probably isn't as generic as you think. Consider refactoring to a more appropriate approach.

Upvotes: 3

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