Java: instanceof Generic

Question

Isn't there any way to find the class-type of a generic?

if (T instanceof String) {     // do something... } 

The above definitely does not compile.

Answer 1

Generics are a compile time feature. Generics add checks at compile time which may not have any meaning at runtime. This is one example. You can only check the type of the object referenced which could be a super type in code. If you want to pass the type T you have do this explicitly.

void someMethod(Class<T> tClass) {     if(String.class.isAssignableFrom(tClass))  

or

void someMethod(Class<T> tClass, T tArg) { 

Note: the type might not be the same,

someMethod(Number.class, 1);