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package bjc.data;
/**
* Represents a 'context' which is a hierarchical set of objects.
* @author Ben Culkin
*
*/
public interface Context {
/**
* Register an object with this context.
*
* @param name The name of the object.
* @param o The object to register.
*/
void register(String name, Object o);
/**
* Get the parent of this context.
*
* @return The parent of this context.
*/
Context getParent();
/**
* Get an object from this context.
*
* @param name The name of the object.
*
* @return The object bound to that name.
*/
Object get(String name);
/**
* Get an object which is an instance of the provided class or a subclass
* thereof.
*
* @param <T> The type of the object.
*
* @param contract The class of the object.
*
* @return An instance of the provided class.
*/
<T> T get(Class<T> contract);
/**
* Get a named object which is an instance of the provided class or a subclass
* thereof.
*
* @param <T> The type of the object.
*
* @param name The name of the object
* @param contract The class of the object.
*
* @return An instance of the provided class, with the given name..
*/
default <T> T get(String name, Class<T> contract) {
Object obj = get(name);
return obj == null
? getParent().get(name, contract)
: contract.cast(obj);
};
}
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