code: package ludiiInterface.games.CFour;
  
  import ludiiInterface.general.SystemConversion;
  
  import java.util.Map;
  import java.util.stream.Collectors;
  import java.util.stream.Stream;
  
  public class SystemConversionC4 extends SystemConversion {
  
      public SystemConversionC4() {
          Map<Integer, Integer> map = Stream.of(new Integer[][] {
                  {-1,-1},{ 0, 0},{ 1, 1},{ 2,2},{ 3,3},{ 4,4},{ 5,5},{ 6,6}
          }).collect(Collectors.toMap(data -> data[0], data -> data[1]));
          indicesMap.putAll(map);
  
          Map<Integer,Integer> playerMapping = Stream.of(new Integer[][] {
                  {1,0}, {2,1}
          }).collect(Collectors.toMap(data ->data[0], data -> data[1]));
          playerMap.putAll(playerMapping);
      }
  
      @Override
      public boolean isValidGBGIndex(int index) {
          return (index>=0 && index <=6);
      }
  
      @Override
      public boolean isValidLudiiIndex(int index) {
          return (index>=0 && index <=6);
      }
  }
  