code: ///////////////////////////////////////////////////////////////////////////
  //                   __                _      _   ________               //
  //                  / /   ____  ____ _(_)____/ | / / ____/               //
  //                 / /   / __ \/ __ `/ / ___/  |/ / / __                 //
  //                / /___/ /_/ / /_/ / / /__/ /|  / /_/ /                 //
  //               /_____/\____/\__, /_/\___/_/ |_/\____/                  //
  //                           /____/                                      //
  //                                                                       //
  //               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.io.graphical;
  
  import java.io.File;
  import java.io.IOException;
  import java.io.OutputStreamWriter;
  import java.io.StringWriter;
  import java.io.Writer;
  import java.nio.charset.StandardCharsets;
  import java.nio.file.Files;
  
  /**
   * An interface for writers of graphical representations of formulas, BDDs, and graphs.
   * @version 2.4.0
   * @since 2.4.0
   */
  public interface GraphicalRepresentationWriter {
  
      /**
       * Writes a given graphical representation with the given writer.
       * @param writer         the writer
       * @param representation the representation to write
       * @throws IOException if there is a problem during writing
       */
      void write(final Writer writer, GraphicalRepresentation representation) throws IOException;
  
      /**
       * Writes a given graphical representation to a file with the given file name.
       * @param fileName       the file name for the output file
       * @param representation the representation to write
       * @throws IOException if there is a problem during writing the file
       */
      default void write(final String fileName, final GraphicalRepresentation representation) throws IOException {
          write(new File(fileName), representation);
      }
  
      /**
       * Writes a given graphical representation to a given file.
       * @param file           the file for the output
       * @param representation the representation to write
       * @throws IOException if there is a problem during writing the file
       */
      default void write(final File file, final GraphicalRepresentation representation) throws IOException {
          try (final Writer writer = new OutputStreamWriter(Files.newOutputStream(file.toPath()), StandardCharsets.UTF_8)) {
              write(writer, representation);
          }
      }
  
      /**
       * Returns the string value of this writer's graphical representation.
       * @param representation the representation
       * @return the string value of the representation
       */
      default String stringValue(final GraphicalRepresentation representation) {
          try (final Writer writer = new StringWriter()) {
              write(writer, representation);
              return writer.toString();
          } catch (final IOException e) {
              throw new IllegalStateException("IO Exception", e);
          }
      }
  }
  