Source for gnu.java.security.util.Sequence

   1: /* Sequence.java -- a sequence of integers.
   2:    Copyright (C) 2004, 2006 Free Software Foundation, Inc.
   3: 
   4: This file is a part of GNU Classpath.
   5: 
   6: GNU Classpath is free software; you can redistribute it and/or modify
   7: it under the terms of the GNU General Public License as published by
   8: the Free Software Foundation; either version 2 of the License, or (at
   9: your option) any later version.
  10: 
  11: GNU Classpath is distributed in the hope that it will be useful, but
  12: WITHOUT ANY WARRANTY; without even the implied warranty of
  13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14: General Public License for more details.
  15: 
  16: You should have received a copy of the GNU General Public License
  17: along with GNU Classpath; if not, write to the Free Software
  18: Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
  19: USA
  20: 
  21: Linking this library statically or dynamically with other modules is
  22: making a combined work based on this library.  Thus, the terms and
  23: conditions of the GNU General Public License cover the whole
  24: combination.
  25: 
  26: As a special exception, the copyright holders of this library give you
  27: permission to link this library with independent modules to produce an
  28: executable, regardless of the license terms of these independent
  29: modules, and to copy and distribute the resulting executable under
  30: terms of your choice, provided that you also meet, for each linked
  31: independent module, the terms and conditions of the license of that
  32: module.  An independent module is a module which is not derived from
  33: or based on this library.  If you modify this library, you may extend
  34: this exception to your version of the library, but you are not
  35: obligated to do so.  If you do not wish to do so, delete this
  36: exception statement from your version.  */
  37: 
  38: 
  39: package gnu.java.security.util;
  40: 
  41: import java.util.AbstractList;
  42: import java.util.LinkedList;
  43: 
  44: /**
  45:  * A monotonic sequence of integers in the finite field 2<sup>32</sup>.
  46:  */
  47: public final class Sequence
  48:     extends AbstractList
  49: {
  50:   private final Integer[] sequence;
  51: 
  52:   /**
  53:    * Create a sequence of integers from 0 to <i>end</i>, with an increment of
  54:    * 1. If <i>end</i> is less than 0, then the sequence will wrap around
  55:    * through all positive integers then negative integers until the end value is
  56:    * reached. Naturally, this will result in an enormous object, so don't do
  57:    * this.
  58:    *
  59:    * @param end The ending value.
  60:    */
  61:   public Sequence(int end)
  62:   {
  63:     this(0, end, 1);
  64:   }
  65: 
  66:   /**
  67:    * Create a sequence of integers from <i>start</i> to <i>end</i>, with an
  68:    * increment of 1. If <i>end</i> is less than <i>start</i>, then the
  69:    * sequence will wrap around until the end value is reached. Naturally, this
  70:    * will result in an enormous object, so don't do this.
  71:    *
  72:    * @param start The starting value.
  73:    * @param end The ending value.
  74:    */
  75:   public Sequence(int start, int end)
  76:   {
  77:     this(start, end, 1);
  78:   }
  79: 
  80:   /**
  81:    * Create a sequence of integers from <i>start</i> to <i>end</i>, with an
  82:    * increment of <i>span</i>. If <i>end</i> is less than <i>start</i>, then
  83:    * the sequence will wrap around until the end value is reached. Naturally,
  84:    * this will result in an enormous object, so don't do this.
  85:    * <p>
  86:    * <i>span</i> can be negative, resulting in a decresing sequence.
  87:    * <p>
  88:    * If <i>span</i> is 0, then the sequence will contain {<i>start</i>,
  89:    * <i>end</i>} if <i>start</i> != <i>end</i>, or just the singleton
  90:    * <i>start</i> if <i>start</i> == <i>end</i>.
  91:    *
  92:    * @param start The starting value.
  93:    * @param end The ending value.
  94:    * @param span The increment value.
  95:    */
  96:   public Sequence(int start, int end, int span)
  97:   {
  98:     if (span == 0)
  99:       {
 100:         if (start != end)
 101:           sequence = new Integer[] { Integer.valueOf(start),
 102:                                      Integer.valueOf(end) };
 103:         else
 104:           sequence = new Integer[] { Integer.valueOf(start) };
 105:       }
 106:     else
 107:       {
 108:         LinkedList l = new LinkedList();
 109:         for (int i = start; i != end; i += span)
 110:           l.add(Integer.valueOf(i));
 111: 
 112:         l.add(Integer.valueOf(end));
 113:         sequence = (Integer[]) l.toArray(new Integer[l.size()]);
 114:       }
 115:   }
 116: 
 117:   public Object get(int index)
 118:   {
 119:     if (index < 0 || index >= size())
 120:       throw new IndexOutOfBoundsException("index=" + index + ", size=" + size());
 121:     return sequence[index];
 122:   }
 123: 
 124:   public int size()
 125:   {
 126:     return sequence.length;
 127:   }
 128: 
 129:   public Object[] toArray()
 130:   {
 131:     return (Object[]) sequence.clone();
 132:   }
 133: }