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package bjc.esodata;
/**
* Represents a hierarchical map.
*
* What's useful about this is that you can hand sub-directories to people and
* be able to ensure that they can't write outside of it.
*
* @param <K>
* The key type of the map.
* @param <V>
* The value type of the map.
*/
public interface Directory<K, V> {
/**
* Retrieves a given sub-directory.
*
* @param key
* The key to retrieve the sub-directory for.
*
* @return The sub-directory under that name.
*
* @throws IllegalArgumentException
* If the given sub-directory doesn't exist.
*/
Directory<K, V> getSubdirectory(K key);
/**
* Check if a given sub-directory exists.
*
* @param key
* The key to look for the sub-directory under.
*
* @return Whether or not a sub-directory of that name exists.
*/
boolean hasSubdirectory(K key);
/**
* Insert a sub-directory into the dictionary.
*
* @param key
* The name of the new sub-directory
* @param value
* The sub-directory to insert
*
* @return The old sub-directory attached to this key, or null if such a
* sub-directory didn't exist
*/
Directory<K, V> putSubdirectory(K key, Directory<K, V> value);
/**
* Create a new sub-directory.
*
* Will fail if a sub-directory of that name already exists.
*
* @param key
* The name of the new sub-directory.
*
* @return The new sub-directory, or null if one by that name already exists.
*/
default Directory<K, V> newSubdirectory(final K key) {
if (hasSubdirectory(key)) return null;
final Directory<K, V> dir = new SimpleDirectory<>();
putSubdirectory(key, dir);
return dir;
}
/**
* Check if the directory contains a data-item under the given key.
*
* @param key
* The key to check for.
*
* @return Whether or not there is a data item for the given key.
*/
boolean containsKey(K key);
/**
* Retrieve a given data-item from the directory.
*
* @param key
* The key to retrieve data for.
*
* @return The value for the given key.
*
* @throws IllegalArgumentException
* If no value exists for the given key.
*/
V getKey(K key);
/**
* Insert a data-item into the directory.
*
* @param key
* The key to insert into.
*
* @param val
* The value to insert.
*
* @return The old value of key, or null if such a value didn't exist.
*/
V putKey(K key, V val);
}
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