Java map with values limited by key's type parameter
- by Ashley Mercer
Is there a way in Java to have a map where the type parameter of a value is tied to the type parameter of a key? What I want to write is something like the following:
public class Foo {
// This declaration won't compile - what should it be?
private static Map<Class<T>, T> defaultValues;
// These two methods are just fine
public static <T> void setDefaultValue(Class<T> clazz, T value) {
defaultValues.put(clazz, value);
}
public static <T> T getDefaultValue(Class<T> clazz) {
return defaultValues.get(clazz);
}
}
That is, I can store any default value against a Class object, provided the value's type matches that of the Class object. I don't see why this shouldn't be allowed since I can ensure when setting/getting values that the types are correct.
EDIT: Thanks to cletus for his answer. I don't actually need the type parameters on the map itself since I can ensure consistency in the methods which get/set values, even if it means using some slightly ugly casts.
