package org.djunits.unit;
   
   import org.djunits.unit.si.SIDimensions;
   import org.djunits.unit.util.UnitException;
   import org.djutils.logger.CategoryLogger;
   
   /**
    * SIUnit describes a unit with arbitrary SI dimensions for which no predefined unit exists.
    * <p>
   * Copyright (c) 2019-2025 Delft University of Technology, PO Box 5, 2600 AA, Delft, the Netherlands. All rights reserved. <br>
   * BSD-style license. See <a href="https://djunits.org/docs/license.html">DJUNITS License</a>
   * </p>
   * @author <a href="https://www.tudelft.nl/averbraeck" target="_blank">Alexander Verbraeck</a>
   */
  public class SIUnit extends Unit<SIUnit>
  {
      /** */
      private static final long serialVersionUID = 20190829L;
  
      /** the SI Unit for dimensionless. */
      public static final SIUnit DIMLESS = SIUnit.of(SIDimensions.DIMLESS);
  
      static
      {
          // make sure all predefined unit types get registered before we start using SIScalars.
          try
          {
              Class.forName("org.djunits.unit.util.UNITS");
          }
          catch (ClassNotFoundException exception)
          {
              CategoryLogger.always().error("Could not find class org.djunits.unit.util.UNITS for initializing SIUnit");
          }
      }
  
      /**
       * Instantiate an SI unit 'of' a String.
       * @param siString the SI string, e.g., "kgm/s2"
       * @return the SIUnit based on the SI dimensionality
       * @throws UnitException when the SI string is not according to the rules
       */
      public static SIUnit of(final String siString) throws UnitException
      {
          return Unit.lookupOrCreateUnitWithSIDimensions(SIDimensions.of(siString));
      }
  
      /**
       * Instantiate an SI unit 'of' a SIDimensions.
       * @param siDimensions the SI dimensions
       * @return the SIUnit based on the SI dimensionality
       */
      public static SIUnit of(final SIDimensions siDimensions)
      {
          return Unit.lookupOrCreateUnitWithSIDimensions(siDimensions);
      }
  
      @Override
      public String toString()
      {
          return getQuantity().getSiDimensions().toString(true, false);
      }
  
      @Override
      @SuppressWarnings("checkstyle:designforextension")
      public int hashCode()
      {
          return getQuantity().getSiDimensions().hashCode();
      }
  
      @Override
      @SuppressWarnings({"checkstyle:designforextension", "checkstyle:needbraces"})
      public boolean equals(final Object obj)
      {
          if (this == obj)
              return true;
          if (obj == null)
              return false;
          if (getClass() != obj.getClass())
              return false;
          SIUnit other = (SIUnit) obj;
          if (!getQuantity().getSiDimensions().equals(other.getQuantity().getSiDimensions()))
              return false;
          return true;
      }
  
  }