Question

I have a class

A<T> {
    T value;
    public T getValue() { return value; }
    public void setValue(T value) { this.value = value;}
}

And try to use it with non-generic method like this:

A<?>[] as = new A<?>[2]; as[0] = new A<Integer>(); as[1] = new A<String>();
for(A<?> a : as) {
    someobj.put(a.getValue()); // <-- got an error "The method put(String) is not applicable for the arguments (capture#2-of ?)"
}

someobj has put(String s), put(Integer i) etc.

How can i do something like dynamic type casting and fix an error?

Answer 1

As explained by Marko, the type of your generic A is lost. But what you could do is to use reflection to invoke the correct “put” method.

Something like this:

A<?>[] as = new A<?>[2]; as[0] = new A<Integer>(); as[1] = new A<String>();
for(A<?> a : as) {
    Method m = someobj.getClass().getMethod("put", a.getValue().getClass());
    m.invoke(somobj, a.getValue());
}