You answered your own question: the Java compiler "erases" these types,
so they are not available to you. It's purely a Java compiler feature,
not part of the JVM.
However, JavaScript can provide a workaround. Just create your own
wrapper (a JavaScript dict) that includes custom type information:
var myList = {};
myList.list = new java.util.ArrayList();
myList.type = String;
You can then can create JavaScript functions that check for the type and
then delegate to this.list:
myList.add = function(value) {
if (!(value instanceof this.type) throw 'Wrong!';
this.list.add(value);
}
Note that if you want to use JavaScript (as opposed to JVM) types, you
must explicitly use their constructor:
myList.add(new String('this will work'))
myLast.add('this won't work')
On 10/27/2015 06:48 PM, James Falkner wrote:
Hey all,
Currently @ JavaOne enjoying the Nashorn talks. But I have a question.
Is it possible to create extended classes using parameterized types?
What I want to do is create these:
class SomeClass extends SomeBaseClass<SomeType> {
...
}
I know parameterized types are mostly a compile-time thing, but they
are encoded into the class bytes and can be accessed in Java using:
ParameterizedType t = (ParameterizedType) clazz.getGenericSuperclass();
Type[] types = parameterizedType.getActualTypeArguments();
So I was wondering if it was possible to instantiate a concrete Java
class from Javascript such that it would appear just as though I had
created it as above?
Using Java.type() and Java.extend() doesn't seem to create the class
in the same way as the Java code with Parameterized types. Thanks!
-James
