net.sf.staccatocommons.collections.stream.impl.internal.AbstractTransformStream Maven / Gradle / Ivy

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/*
 Copyright (c) 2011, The Staccato-Commons Team

 This program is free software; you can redistribute it and/or modify
 it under the terms of the GNU Lesser General Public License as published by
 the Free Software Foundation; version 3 of the License.

 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU Lesser General Public License for more details.
 */
package net.sf.staccatocommons.collections.stream.impl.internal;

import java.util.List;

import net.sf.staccatocommons.collections.stream.AbstractStream;
import net.sf.staccatocommons.collections.stream.Stream;
import net.sf.staccatocommons.defs.Thunk;
import net.sf.staccatocommons.iterators.thriter.Thriterator;
import net.sf.staccatocommons.lang.tuple.Pair;
import net.sf.staccatocommons.restrictions.check.NonNull;

/**
 * @author flbulgarelli
 */
public abstract class AbstractTransformStream extends AbstractStream {

  private final Stream stream;
  private Stream streamCached;

  /**
   * Creates a new {@link AbstractTransformStream}
   */
  public AbstractTransformStream(@NonNull Stream stream) {
    this.stream = stream;
  }

  @Override
  public final Thriterator iterator() {
    return applyCached().iterator();
  }

  @Override
  public final B get(int n) {
    return applyCached().get(n);
  }

  @Override
  public final Pair, Stream> delayedDecons() {
    return applyCached().delayedDecons();
  }

  @Override
  public final boolean isEmpty() {
    return applyCached().isEmpty();
  }

  public final int size() {
    return applyCached().size();
  }

  @Override
  public final List toList() {
    return applyCached().toList();
  }

  private Stream applyCached() {
    if (streamCached == null)
      streamCached = apply();
    return streamCached;
  }

  protected abstract Stream apply();

  /**
   * @return the stream
   */
  protected Stream getStream() {
    return stream;
  }

}