code: ///////////////////////////////////////////////////////////////////////////
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  //                  / /   ____  ____ _(_)____/ | / / ____/               //
  //                 / /   / __ \/ __ `/ / ___/  |/ / / __                 //
  //                / /___/ /_/ / /_/ / / /__/ /|  / /_/ /                 //
  //               /_____/\____/\__, /_/\___/_/ |_/\____/                  //
  //                           /____/                                      //
  //                                                                       //
  //               The Next Generation Logic Library                       //
  //                                                                       //
  ///////////////////////////////////////////////////////////////////////////
  //                                                                       //
  //  Copyright 2015-20xx Christoph Zengler                                //
  //                                                                       //
  //  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.logicng.handlers;
  
  import org.logicng.datastructures.Assignment;
  
  /**
   * Interface for a handler for MaxSAT solvers.
   * @version 2.1.0
   * @since 1.0
   */
  public interface MaxSATHandler extends Handler {
  
      /**
       * Returns a SAT handler which can be used to cancel internal SAT calls of the MaxSAT solver.
       * @return a SAT handler
       */
      SATHandler satHandler();
  
      @Override
      default boolean aborted() {
          return satHandler() != null && satHandler().aborted();
      }
  
      /**
       * This method is called when the MaxSAT solver found a new lower bound for a solution.
       * @param lowerBound the cost of the lower bound
       * @param model      the model of the lower bound, may be null if not applicable
       * @return {@code true} if the solving process should be continued, otherwise {@code false}
       */
      boolean foundLowerBound(final int lowerBound, final Assignment model);
  
      /**
       * This method is called when the MaxSAT solver found a new upper bound for a solution.
       * @param upperBound the cost of the upper bound
       * @param model      the model of the upper bound, may be null if not applicable
       * @return {@code true} if the solving process should be continued, otherwise {@code false}
       */
      boolean foundUpperBound(final int upperBound, final Assignment model);
  
      /**
       * This method is called when the MaxSAT solver finished solving.
       */
      default void finishedSolving() {
  
      }
  
      /**
       * Returns the last approximation of the result or -1 if there is no approximation for the lower bound.
       * If the handler does not cancel the solving process, it is not guaranteed that this
       * method will return the optimal result. Use the respective method of the MaxSAT solver instead.
       * @return the last approximation of the result or -1 if no approximation is known
       */
      int lowerBoundApproximation();
  
      /**
       * Returns the last approximation of the result or -1 if there is no approximation for the lower bound.
       * If the handler does not cancel the solving process, it is not guaranteed that this
       * method will return the optimal result. Use the respective method of the MaxSAT solver instead.
       * @return the last approximation of the result or -1 if no approximation is known
       */
      int upperBoundApproximation();
  }
  