guava/src/com/google/common/collect/TransformedIterator.java


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/*
 * Copyright (C) 2012 The Guava Authors
 *
 * Licensed 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 com.google.common.collect;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.GwtCompatible;

import java.util.Iterator;

/**
 * An iterator that transforms a backing iterator; for internal use. This avoids
 * the object overhead of constructing a {@link Function} for internal methods.
 *
 * @author Louis Wasserman
 */
@GwtCompatible
abstract class TransformedIterator<F, T> implements Iterator<T> {
  final Iterator<? extends F> backingIterator;

  TransformedIterator(Iterator<? extends F> backingIterator) {
    this.backingIterator = checkNotNull(backingIterator);
  }

  abstract T transform(F from);

  @Override
  public final boolean hasNext() {
    return backingIterator.hasNext();
  }

  @Override
  public final T next() {
    return transform(backingIterator.next());
  }

  @Override
  public final void remove() {
    backingIterator.remove();
  }
}