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Special Java 1.8+ Library with extended collection related functionality
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/**
 * Copyright (C) 2014-2020 Philip Helger (www.helger.com)
 * philip[at]helger[dot]com
 *
 * 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.helger.collection.safe;

import java.util.function.Supplier;

import javax.annotation.Nonnegative;
import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import javax.annotation.concurrent.ThreadSafe;

import com.helger.commons.ValueEnforcer;
import com.helger.commons.annotation.MustImplementEqualsAndHashcode;
import com.helger.commons.collection.impl.CommonsVector;
import com.helger.commons.functional.ISupplier;
import com.helger.commons.hashcode.HashCodeGenerator;
import com.helger.commons.string.ToStringGenerator;

/**
 * This is a specialized {@link CommonsVector} that can handle read accesses on
 * list items that are not yet in the container. If {@link #get(int)} is called
 * with an index that would normally throw an
 * {@link ArrayIndexOutOfBoundsException} this class will fill all indices
 * between the current {@link #size()} and the desired index with values
 * provided by an {@link ISupplier}. If you don't pass an {@link ISupplier} in
 * the constructor a default factory returning null values is used.
 *
 * @author Philip
 * @param 
 *        The type of the elements in the list
 */
@ThreadSafe
public class SafeVector  extends CommonsVector 
{
  @MustImplementEqualsAndHashcode
  private final ISupplier  m_aFactory;

  /**
   * Constructor filling up the missing elements with null values.
   */
  public SafeVector ()
  {
    this ( () -> null);
  }

  /**
   * Constructor with a custom factory to fill the missing elements.
   *
   * @param aFactory
   *        The factory to use. May not be null.
   */
  public SafeVector (@Nonnull final ISupplier  aFactory)
  {
    m_aFactory = ValueEnforcer.notNull (aFactory, "Factory");
  }

  /**
   * @return The factory for filling missing values as provided in the
   *         constructor.
   */
  @Nonnull
  public ISupplier  getFactory ()
  {
    return m_aFactory;
  }

  private void _ensureSize (@Nonnegative final int nIndex)
  {
    // fill the gap
    final int nGap = nIndex - size () + 1;
    for (int i = 0; i < nGap; ++i)
      add (m_aFactory.get ());
  }

  @Override
  public synchronized ELEMENTTYPE get (@Nonnegative final int nIndex)
  {
    _ensureSize (nIndex);
    return super.get (nIndex);
  }

  @Nullable
  public synchronized ELEMENTTYPE computeIfAbsent (@Nonnegative final int nIndex, @Nonnull final Supplier  aFactory)
  {
    _ensureSize (nIndex);
    ELEMENTTYPE ret = super.get (nIndex);
    if (ret == null)
    {
      ret = aFactory.get ();
      super.set (nIndex, ret);
    }
    return ret;
  }

  @Override
  public synchronized ELEMENTTYPE set (@Nonnegative final int nIndex, @Nonnull final ELEMENTTYPE aElement)
  {
    _ensureSize (nIndex);
    return super.set (nIndex, aElement);
  }

  @Override
  public synchronized boolean equals (final Object o)
  {
    if (o == this)
      return true;
    // Special case because this check is not performed in super.equals
    if (o == null || !getClass ().equals (o.getClass ()))
      return false;
    if (!super.equals (o))
      return false;
    final SafeVector  rhs = (SafeVector ) o;
    return m_aFactory.equals (rhs.m_aFactory);
  }

  @Override
  public synchronized int hashCode ()
  {
    return HashCodeGenerator.getDerived (super.hashCode ()).append (m_aFactory).getHashCode ();
  }

  @Override
  public synchronized String toString ()
  {
    return ToStringGenerator.getDerived (super.toString ()).append ("factory", m_aFactory).getToString ();
  }
}