How can i achieve this?
public class GenericClass<T>
{
public Type getMyType()
{
//How do I return the type of T?
}
}
Everything I have tried so far always returns type Object rather than the specific type used.
Thanks a lot.
I want to use enum values in a selectManyCheckbox. The checkboxes get populated correctly, however, when selecting some values and submitting them, their runtime type is String, and not enum. My code:
<h:selectManyCheckbox value="#{userController.roles}" layout="pageDirection">
<f:selectItems value="#{userController.rolesSelectMany}" />
</h:selectManyCheckbox>
UserCont...
I wish to a check if a method exists in an interface based on its signatures.
The signature that the method should have is:
Collection<Foo> methodName(Spam arg0, Eggs arg1, ...)
I can find the methods via Class.getMethods()
then find the name, parameters and return type respectively with method.getName(), method.getParameterTypes() and method.getReturnType().
But what do I compare ...
I have been trying to determine the type of a field in a class. I've seen all the introspection methods but haven't quite figured out how to do it. This is going to be used to generate xml/json from a java class. I've looked at a number of the questions here but haven't found exactly what I need.
Example:
class Person {
public final String name;
public final List<Person> childre...
Typically, I've seen people use the class literal like this:
Class<Foo> cls = Foo.class;
But what if the type is generic, e.g. List? This works fine, but has a warning since List should be parameterized:
Class<List> cls = List.class
So why not add a <?>? Well, this causes a type mismatch error:
Class<List<?>> cls = List.class
I figured something like this ...
Type erasure is supposed to erase all generic information...
If this is the case how does a library like GSON use generics to determine what type to deserialize to?
e.g.
private Map<String,Date> tenordates;
This will deserialize to <String,Date>
where as
private Map<Date,Date> tenordates;
will deserialize to <Date,Date>
so somehow its using the generic info at ru...
How can I print the type of a generic java type?
Reflection? Any tricks?
public class Foo<K> {
private K element;
@Override
public String toString() {
return "Type: " + K;
}
}
In Java, Class has an isAssignableFrom method defined as follows:
public boolean isAssignableFrom(Class<?> cls)
Determines if the class or interface represented by this Class object is either the same as, or is a superclass or superinterface of, the class or interface represented by the specified Class parameter. It returns true if so; otherwise it returns false. If this Class obj...
Given two classes like this:
class Example1<A,B> {
public Map<A,B> someMap = new HashMap<A,B>();
}
class Example2 extends Example1<URL, URL> {
}
Is there any way using reflection that I can determine the component types of the Map for Example2?
I know I can do:
ParameterizedType t = (ParameterizedType) Example2.class.getFields()[0].getGenericType();
But f...
I wrote a class that has a map of <String, Object>. I need it to hold arbitrary objects, but at the same time sometimes I need to cast some of those objects, so I'll do something like
HashMap<String, Object> map = new HashMap<String, Object>();
Object foo = map.get("bar"); ...
This is my code:
The ExecutorImp extends AbstractExecutor which extract the same execute logics of its implementers(ExecutorImp is one case),when calling the execute() method of ExecutorImp, it will call the method in its supertype,but the supertype (the AbstractExcutor) should know another class binding to the implementer(in the example, it is the User class):
import java.lang.reflect.Invocat...
I have an interface
public interface FooBar<T> { }
I have a class that implements it
public class BarFoo implements FooBar<Person> { }
With reflection, I want to take an instance of BarFoo and get that the version of FooBar it implements is Person.
I use .getInterfaces from BarFoo to get back to FooBar, but that doesn't help me find out what T is.
There are other related questions e.g. 6624113, 3403909, 4516891 but my question is simpler and more specific.
I want to know at runtime what type my class was parameterized with - I want a Class object of the type of the type parameter. Because of type erasure, the expression T.class doesn't work, and there is no function like typeof(T) in C# to get it.
However, there is some "uber-reflecti...
I am using reflection to get all the get all the methods in a class like this:
Method[] allMethods = c.getDeclaredMethods();
After that I am iterating through the methods
for (Method m: allMethods){
//I want to find out if the return is is a parameterized type or not
m.getReturnType();
}
For example: if I have a method like this one:
public Set<Cat> getCats();
How can I u...
I'm running into a problem with my program where given an object and an attribute name I want to return the method's return type.
public static Class<?> getAttributeType(Object object, String attributeName) {
try {
Method method = object.getClass().getMethod(
"get" + StringUtils.capitalize(attributeName));
return method.getReturnType();
} catch (...
