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'rapiddweller Common' is an open source Java library forked from Databene Commons by Volker Bergmann. It provides extensions to the Java core library by utility classes, abstract concepts and concrete implementations.

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/*
 * Copyright (C) 2004-2015 Volker Bergmann ([email protected]).
 * 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 com.rapiddweller.common.visitor;

import com.rapiddweller.common.ComparableComparator;
import com.rapiddweller.common.Element;
import com.rapiddweller.common.Visitor;

import java.util.Comparator;

/**
 * Utility that navigates Elements with the Visitor Pattern and
 * uses a Comparator for determining a minimum or maximum value in the graph.
 * Created: 04.02.2007 08:50:13
 *
 * @param  the type of the elements to examine
 * @author Volker Bergmann
 */
public class ExtremeElementFinder {

  /**
   * Find max e.
   *
   * @param   the type parameter
   * @param root the root
   * @return the e
   */
  public static > E findMax(Element root) {
    return findMax(root, new ComparableComparator<>());
  }

  /**
   * Find max e.
   *
   * @param         the type parameter
   * @param root       the root
   * @param comparator the comparator
   * @return the e
   */
  public static  E findMax(Element root, Comparator comparator) {
    return findExtreme(root, comparator, 1);
  }

  /**
   * Find min e.
   *
   * @param   the type parameter
   * @param root the root
   * @return the e
   */
  public static > E findMin(Element root) {
    return findMin(root, new ComparableComparator<>());
  }

  /**
   * Find min e.
   *
   * @param         the type parameter
   * @param root       the root
   * @param comparator the comparator
   * @return the e
   */
  public static  E findMin(Element root, Comparator comparator) {
    return findExtreme(root, comparator, -1);
  }

  private static  E findExtreme(Element root, Comparator comparator, int extreme) {
    ExtremeVisitor visitor = new ExtremeVisitor<>(comparator, extreme);
    root.accept(visitor);
    return visitor.extremeElement;
  }

  /**
   * The type Extreme visitor.
   *
   * @param  the type parameter
   */
  static final class ExtremeVisitor implements Visitor {

    private final Comparator comparator;
    private final int extreme;
    /**
     * The Extreme element.
     */
    E extremeElement;

    /**
     * Instantiates a new Extreme visitor.
     *
     * @param comparator the comparator
     * @param extreme    the extreme
     */
    public ExtremeVisitor(Comparator comparator, int extreme) {
      this.comparator = comparator;
      this.extreme = extreme;
      this.extremeElement = null;
    }

    @Override
    public  void visit(C element) {
      if (extremeElement == null || comparator.compare(element, extremeElement) == extreme) {
        extremeElement = element;
      }
    }
  }
}