Mercurial > hg > blitz_condensed
annotate src/org/dancres/struct/LinkedInstances.java @ 0:3dc0c5604566
Initial checkin of blitz 2.0 fcs - no installer yet.
author | Dan Creswell <dan.creswell@gmail.com> |
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date | Sat, 21 Mar 2009 11:00:06 +0000 |
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0
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1 package org.dancres.struct; |
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2 |
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3 import java.io.Serializable; |
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4 import java.util.List; |
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5 import java.util.ArrayList; |
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6 |
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7 /** |
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8 In most general situations one might store a number of instances in a |
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9 java.util.LinkedList or similar but this has an overhead as we create |
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10 a holder object for each instance we add - i.e. we're delegating the |
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11 management of being in the list to this holder object. This has two |
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12 disadvantages: |
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13 |
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14 <OL> |
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15 <LI> Memory overhead - we have two objects per object we wish to hold. </LI> |
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16 <LI> Lack of direct addressability - having obtained a reference to an |
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17 object we might like to use that directly to access members of the list. |
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18 </LI> |
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19 </OL> |
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20 |
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21 User is expected to provide suitable multi-threaded protection. |
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22 */ |
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23 public class LinkedInstances implements Serializable { |
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24 private LinkedInstance theHead; |
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25 private LinkedInstance theTail; |
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26 |
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27 private int theTotalInstances = 0; |
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28 |
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29 public LinkedInstances() { |
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30 } |
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31 |
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32 public LinkedInstance getHead() { |
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33 return theHead; |
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34 } |
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35 |
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36 public LinkedInstance getTail() { |
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37 return theTail; |
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38 } |
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39 |
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40 public List copy() { |
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41 ArrayList myMembers = new ArrayList(); |
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42 |
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43 LinkedInstance myInstance = theHead; |
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44 while (myInstance != null) { |
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45 myMembers.add(myInstance); |
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46 |
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47 myInstance = myInstance.getNext(); |
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48 } |
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49 |
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50 return myMembers; |
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51 } |
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52 |
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53 public void insert(LinkedInstance aLink) { |
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54 aLink.setNext(null); |
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55 aLink.setPrev(null); |
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56 |
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57 if (theHead == null) { |
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58 theHead = theTail = aLink; |
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59 } else { |
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60 theHead.setPrev(aLink); |
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61 aLink.setNext(theHead); |
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62 theHead = aLink; |
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63 } |
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64 |
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65 ++theTotalInstances; |
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66 } |
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67 |
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68 public void add(LinkedInstance aLink) { |
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69 aLink.setNext(null); |
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70 aLink.setPrev(null); |
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71 |
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72 if (theHead == null) { |
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73 theHead = theTail = aLink; |
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74 } else { |
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75 theTail.setNext(aLink); |
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76 aLink.setPrev(theTail); |
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77 theTail = aLink; |
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78 } |
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79 |
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80 ++theTotalInstances; |
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81 } |
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82 |
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83 public void remove(LinkedInstance aLink) { |
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84 LinkedInstance myPrev = aLink.getPrev(); |
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85 LinkedInstance myNext = aLink.getNext(); |
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86 |
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87 if (myPrev != null) |
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88 myPrev.setNext(myNext); |
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89 else |
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90 theHead = myNext; |
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91 |
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92 if (myNext != null) |
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93 myNext.setPrev(myPrev); |
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94 else |
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95 theTail = myPrev; |
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96 |
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97 --theTotalInstances; |
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98 |
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99 aLink.setPrev(null); |
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100 aLink.setNext(null); |
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101 } |
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102 |
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103 public LinkedInstance removeLast() { |
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104 LinkedInstance myLast = theTail; |
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105 theTail = myLast.getPrev(); |
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106 |
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107 if (theTail != null) |
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108 theTail.setNext(null); |
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109 else |
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110 theHead = null; |
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111 |
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112 myLast.setPrev(null); |
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113 myLast.setNext(null); |
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114 |
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115 --theTotalInstances; |
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116 |
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117 return myLast; |
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118 } |
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119 |
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120 public int getSize() { |
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121 return theTotalInstances; |
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3dc0c5604566
Initial checkin of blitz 2.0 fcs - no installer yet.
Dan Creswell <dan.creswell@gmail.com>
parents:
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