content: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to you 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.apache.calcite.runtime;
  
  /**
   * Synthetic record with zero fields.
   *
   * <p>Since all instances are identical, {@code Unit} is a singleton.
   */
  public class Unit implements Comparable<Unit> {
    public static final Unit INSTANCE = new Unit();
  
    private Unit() {
    }
  
    @Override public int compareTo(Unit that) {
      return 0;
    }
  
    @Override public String toString() {
      return "{}";
    }
  }
  