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.cassandra.service.accord;
  
  import javax.annotation.Nullable;
  
  public abstract class ImmutableAccordSafeState<K, V> implements AccordSafeState<K, V>
  {
      protected final K key;
      @Nullable
      protected V original;
      protected boolean invalidated;
  
      protected ImmutableAccordSafeState(K key)
      {
          this.key = key;
      }
  
      @Override
      public K key()
      {
          return key;
      }
  
      @Override
      public V original()
      {
          checkNotInvalidated();
          return original;
      }
  
      @Override
      public V current()
      {
          checkNotInvalidated();
          return original;
      }
  
      @Override
      public void invalidate()
      {
          invalidated = true;
      }
  
      @Override
      public boolean invalidated()
      {
          return invalidated;
      }
  
      @Override
      public void set(V update)
      {
          throw new UnsupportedOperationException();
      }
  
      @Override
      public void revert()
      {
          checkNotInvalidated();
      }
  }
  