Java: Instanceof and Generics

The error message says it all. At runtime, the type is gone, there is no way to check for it.

You could catch it by making a factory for your object like this:

public static <T> MyObject<T> createMyObject(Class<T> type) {
    return new MyObject<T>(type);
}

And then in the object’s constructor store that type, so variable so that your method could look like this:

if (arg0 != null && !(this.type.isAssignableFrom(arg0.getClass())) {
    return -1;
}