Java Collection - 如何将Wrapper值数组列表转换为基本数组

/*******************************************************************************
 * Copyright (C) 2005, 2011  Wolfgang Schramm and Contributors
 * 
 * This program is free software; you can redistribute it and/or modify it under
 * the terms of the GNU General Public License as published by the Free Software
 * Foundation version 2 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 General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110, USA
 *******************************************************************************/
package net.tourbook.common.util;

import java.util.ArrayList;

public class ArrayListToArray {

  /**
   * Converts an Integer array list into an doublearray
   * 
   * @param list
   * @return
   */
  final public static double[] integerToDouble(final ArrayList<Integer> list) {
    
    final double[] returnArray = new double[list.size()];
    int valueIndex = 0;
    
    for (final Integer value : list) {
      returnArray[valueIndex++] = value;
    }
    
    return returnArray;
  }

  /**
   * Converts an Integer array list into an float array
   * 
   * @param list
   * @return
   */
  final public static float[] integerToFloat(final ArrayList<Integer> list) {

    final float[] returnArray = new float[list.size()];
    int valueIndex = 0;

    for (final Integer value : list) {
      returnArray[valueIndex++] = value;
    }

    return returnArray;
  }

  /**
   * Converts an Float array list into an float array
   * 
   * @param list
   * @return
   */
  final public static float[] toFloat(final ArrayList<Float> list) {

    final float[] returnArray = new float[list.size()];
    int valueIndex = 0;

    for (final Float value : list) {
      returnArray[valueIndex++] = value;
    }

    return returnArray;
  }

  /**
   * converts an Integer array list into an int array
   * 
   * @param list
   * @return
   */
  final public static int[] toInt(final ArrayList<Integer> list) {

    final int[] returnInt = new int[list.size()];
    int valueIndex = 0;

    for (final Integer value : list) {
      returnInt[valueIndex++] = value;
    }

    return returnInt;
  }

  /**
   * converts an Long array list into a long array
   * 
   * @param list
   * @return
   */
  final public static long[] toLong(final ArrayList<Long> list) {

    final long[] returnLong = new long[list.size()];
    int iValue = 0;

    for (final Long value : list) {
      if (value == null) {
        returnLong[iValue++] = -1;
      } else {
        returnLong[iValue++] = value;
      }
    }

    return returnLong;
  }
}