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 io.jafka.utils;
  
  import java.util.Iterator;
  import java.util.NoSuchElementException;
  
  /**
   * a template for object iterator
   *
   * @author adyliu (imxylz@gmail.com)
   * @since 1.0
   */
  public abstract class IteratorTemplate<T> implements Iterator<T> {
  
      enum State {
          DONE, READY, NOT_READY, FAILED;
      }
  
      private State state = State.NOT_READY;
  
      private T nextItem = null;
  
      public T next() {
          if (!hasNext()) throw new NoSuchElementException();
          state = State.NOT_READY;
          return nextItem;
      }
  
      public boolean hasNext() {
          switch (state) {
              case FAILED:
                  throw new IllegalStateException("Iterator is in failed state");
              case DONE:
                  return false;
              case READY:
                  return true;
              case NOT_READY:
                  break;
          }
          return maybeComputeNext();
      }
  
      protected abstract T makeNext();
  
      private boolean maybeComputeNext() {
          state = State.FAILED;
          nextItem = makeNext();
          if (state == State.DONE) return false;
          state = State.READY;
          return true;
      }
  
      public void remove() {
          throw new UnsupportedOperationException();
      }
  
      protected void resetState() {
          state = State.NOT_READY;
      }
  
      protected T allDone() {
          state = State.DONE;
          return null;
      }
  }
  