com.phloc.commons.parent.IChildrenProvider Maven / Gradle / Ivy
/**
* Copyright (C) 2006-2015 phloc systems
* http://www.phloc.com
* office[at]phloc[dot]com
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.phloc.commons.parent;
import java.util.Collection;
import javax.annotation.Nonnegative;
import javax.annotation.Nullable;
/**
* This interface can be used to generically resolved children of a certain
* object.
*
* @author Philip Helger
* @param
* The type of the children to retrieve.
*/
public interface IChildrenProvider
{
/**
* Check if an item has children.
*
* @param aCurrent
* The object to determine the children of. No null or
* non- null constraint possible.
* @return true if this item has children, false
* otherwise.
*/
boolean hasChildren (CHILDTYPE aCurrent);
/**
* @param aCurrent
* The object to determine the children count of. No null
* or non- null constraint possible.
* @return The number of contained direct children. Always ≥ 0.
*/
@Nonnegative
int getChildCount (CHILDTYPE aCurrent);
/**
* Get the children of the passed object.
*
* @param aCurrent
* The object to determine the children of. No null or
* non- null constraint possible.
* @return The child objects, or null if there are no children.
* If null is passed, the resolver is expected to return
* any possible top level (root) elements. This method may NOT return
* null if the call to {@link #hasChildren(Object)} with
* the same object returned true.
*/
@Nullable
Collection getChildren (CHILDTYPE aCurrent);
}