core/functional/src/main/java/org/qi4j/functional/HierarchicalVisitor.java

/*
 * Copyright (c) 2012, Niclas Hedhman. All Rights Reserved.
 *
 * 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 org.qi4j.functional;

/**
 * Visitor to visit hierarchies.
 */
public interface HierarchicalVisitor<NODE, LEAF, ThrowableType extends Throwable> extends Visitor<LEAF, ThrowableType>
{
    /**
     * Enter an instance of T
     *
     * @param visited the visited instance which is now entered
     *
     * @return true if the visitor pattern should continue, false if it should be aborted for this level
     *
     * @throws ThrowableType if an exception occurred during processing. Any client call that initiated the visiting should
     *                       get the exception in order to handle it properly.
     */
    boolean visitEnter( NODE visited )
        throws ThrowableType;

    /**
     * Leave an instance of T
     *
     * @param visited the visited instance which is now left
     *
     * @return true if the visitor pattern should continue, false if it should be aborted for the level of this node
     *
     * @throws ThrowableType if an exception occurred during processing. Any client call that initiated the visiting should
     *                       get the exception in order to handle it properly.
     */
    boolean visitLeave( NODE visited )
        throws ThrowableType;

    @Override
    boolean visit( LEAF visited )
        throws ThrowableType;
}