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    • it.tidalwave.role.Composite Maven / Gradle / Ivy

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    /***********************************************************************************************************************
 *
 * These Foolish Things - Miscellaneous utilities
 * Copyright (C) 2009-2011 by Tidalwave s.a.s. (http://www.tidalwave.it)
 *
 ***********************************************************************************************************************
 *
 * 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.
 *
 ***********************************************************************************************************************
 *
 * WWW: http://thesefoolishthings.java.net
 * SCM: https://bitbucket.org/tidalwave/thesefoolishthings-src
 *
 **********************************************************************************************************************/
package it.tidalwave.role;

import javax.annotation.Nonnull;
import java.util.Collections;
import java.util.List;
import it.tidalwave.util.Finder;
import it.tidalwave.util.NotFoundException;
import it.tidalwave.util.spi.FinderSupport;

/***********************************************************************************************************************
 * 
 * The role of a composite object, that is an object which contains children.
 * 
 * @author  Fabrizio Giudici
 * @version $Id$
 * @it.tidalwave.javadoc.stable
 *
 **********************************************************************************************************************/
public interface Composite>
  {
    //@bluebook-begin other
    public static final Class Composite = Composite.class;

    static class EmptyFinder extends FinderSupport
      {
        @Override @Nonnull
        protected List computeResults() 
          {
            return Collections.emptyList();
          }
      }
    
    /*******************************************************************************************************************
     * 
     * A default Composite with no children.
     *
     ******************************************************************************************************************/
    public final static Composite> DEFAULT = new Composite>() 
      {
        private final Finder EMPTY_FINDER = new EmptyFinder(); // TODO: move to Finder
        
        @Override @Nonnull
        public Finder findChildren() 
          {
            return EMPTY_FINDER;
          }
      };
    
    //@bluebook-end other
    /*******************************************************************************************************************
     * 
     * Returns the children of this object.
     * 
     * @return  the children
     *
     ******************************************************************************************************************/
    @Nonnull
    public SpecializedFinder findChildren();
    //@bluebook-begin other
    //@bluebook-begin visitor
    
    /*******************************************************************************************************************
     * 
     *
     ******************************************************************************************************************/
    public static interface Visitor 
      {
        /***************************************************************************************************************
         * 
         * Visits an object. This method is called before visiting children (pre-order).
         * 
         * @param  object  the visited object
         *
         **************************************************************************************************************/
        public void preVisit (@Nonnull T object);

        /***************************************************************************************************************
         * 
         * Visits an object. This method is actually called just after {@link #preVisit()}, it makes sense to implement
         * it when you don't need to distinguish between pre-order and post-order traversal.
         * 
         * @param  object  the visited object
         *
         **************************************************************************************************************/
        public void visit (@Nonnull T object);

        /***************************************************************************************************************
         * 
         * Visits an object. This method is called after visiting children (post-order).
         * 
         * @param  object  the visited object
         *
         **************************************************************************************************************/
        public void postVisit (@Nonnull T object);

        /***************************************************************************************************************
         * 
         * Returns the value of this visitor.
         * 
         * @return                     the value
         * @throws  NotFoundException  when no value has been found
         *
         **************************************************************************************************************/
        @Nonnull 
        public R getValue()
          throws NotFoundException;
      }
    //@bluebook-end visitor
    
    /*******************************************************************************************************************
     * 
     * A support class for {@link Visitor} which provides default empty methods.
     *
     ******************************************************************************************************************/
    public static class VisitorSupport implements Visitor
      {
        /** {@inheritDoc} */
        public void preVisit (final @Nonnull T object) 
          {            
          }

        /** {@inheritDoc} */
        public void visit (final @Nonnull T object)
          {            
          }

        /** {@inheritDoc} */
        public void postVisit (final @Nonnull T object)
          {            
          }

        /** {@inheritDoc} */
        @Nonnull 
        public R getValue()
          throws NotFoundException
          {
            throw new NotFoundException("Must be implemented by subclasses");  
          }
      }
    //@bluebook-end other
  }
    
    
    
    

    




    
    
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