CBArray


1   package com.ca.commons.cbutil;
2   
3   import java.util.Enumeration  ;
4   import java.util.Vector  ;
5   
6   
7   /**
8    * Utility class for array operations.  Not particularly
9    * fast - most operations implemented as linear searches.
10   * XXX most of these may be redundant - see java 'util.Array' class...
11   *
12   * @author Chris Betts
13   */
14  
15  
16  public class CBArray
17  {
18  
19      /**
20       * Returns the list of elements that appear at least once
21       * in one of the passed arrays.  An element appearing in
22       * both arrays only appears once in the final array.
23       * Behaviour is undefined if Elements are repeated within
24       * an array; they may be trimmed, or not.
25       *
26       * @param a the first array to unionise
27       * @param b the second array to unionise.
28       * @return the resultant union.
29       */
30  
31      public static Object  [] union(Object  [] a, Object  [] b)
32      {
33  //System.out.println("union starting; lengths " + a.length + " and " + b.length);    
34          Object  [] temp = new Object  [a.length + b.length];
35          int i = 0;
36          for (i = 0; i < a.length; i++) temp[i] = a[i];
37          for (int j = 0; j < b.length; j++)
38              if (contains(a, b[j]) == false)   // no duplicates
39                  temp[i++] = b[j];
40                  
41  //for (int k=0; k<i; k++)
42  //    System.out.println("   " + k + " " + temp[k].toString());                
43                  
44          if (a.length + b.length == i)
45              return temp;
46          else
47          {
48              Object  [] ret = new Object  [i];
49              for (int k = 0; k < i; k++) ret[k] = temp[k];
50  
51              return ret;
52          }
53      }
54  
55      /**
56       * Returns the list of elements that appear in a but
57       * not in b.
58       * Behaviour is undefined if Elements are repeated within
59       * an array; they may be trimmed, or not.
60       *
61       * @param a the primary array
62       * @param b the array to 'subtract'.
63       * @return the resultant difference.
64       */
65  
66      public static Object  [] difference(Object  [] a, Object  [] b)
67      {
68  //System.out.println("difference starting; lengths " + a.length + " and " + b.length);    
69          if (a == null || b == null) return null;
70          if (a.length == 0) return ((Object  []) a.clone());
71          if (b.length == 0) return ((Object  []) a.clone());
72  
73          Object  [] temp = new Object  [a.length];
74          int len = 0;
75          for (int i = 0; i < a.length; i++)
76              if (contains(b, a[i]) == false)
77                  temp[len++] = a[i];
78  
79          Object   ret[] = new Object  [len];
80          for (int i = 0; i < len; i++) ret[i] = temp[i];
81          
82  //for (int k=0; k<len; k++)
83  //    System.out.println("   " + k + " " + ret[k].toString() + " (" + ret.getClass().toString() + ")");         
84          
85          return ret;
86      }
87  
88      /**
89       * Returns the list of elements that appear in both
90       * of the passed arrays.  An element appearing in
91       * both arrays only appears once in the final array.
92       * Behaviour is undefined if Elements are repeated within
93       * an array; they may be trimmed, or not.
94       *
95       * @param a the first array to unionise
96       * @param b the second array to unionise.
97       * @return the resultant union.
98       */
99  
100     public static Object  [] intersection(Object  [] a, Object  [] b)
101     {
102 //System.out.println("intersection starting; lengths " + a.length + " and " + b.length);    
103         if (a == null || b == null) return null;
104         if (a.length == 0) return ((Object  []) a.clone());
105         if (b.length == 0) return ((Object  []) b.clone());
106 
107         if (a.length > b.length)            // make a the smallest array
108         {
109             Object  [] c = a;
110             a = b;
111             b = c;
112         }
113 
114         Object  [] temp = new Object  [a.length];
115 
116         int len = 0;
117         for (int i = 0; i < a.length; i++)
118             if (contains(b, a[i]) == true) temp[len++] = a[i];
119 
120         Object  [] ret = new Object  [len];
121         for (int i = 0; i < len; i++) ret[i] = temp[i];
122         return ret;
123     }
124 
125     /**
126      * Returns true if arrays have the same elements, in the same
127      * order.
128      */
129 
130     public static boolean isOrderedEqual(Object  [] a, Object  [] b)
131     {
132         if (a == null && b == null) return true;
133         if (a == null || b == null) return false;
134         if (a.length != b.length) return false;
135         for (int i = 0; i < a.length; i++)
136             if (a[i].equals(b[i]) == false) return false;
137         return true;
138     }
139 
140     /**
141      * Returns true if arrays have the same elements, in any
142      * order.  Does *not* check for different numbers of
143      * repeating elements - i.e. {A,A,B} == {A,B,B} is true.
144      */
145     public static boolean isUnorderedEqual(Object  [] a, Object  [] b)
146     {
147         if (a == null && b == null) return true;
148         if (a == null || b == null) return false;
149         if (a.length != b.length) return false;
150         for (int i = 0; i < a.length; i++)
151             if (contains(b, a[i]) == false) return false;
152         return true;
153     }
154 
155     /**
156      * Returns true if the passed object is not null,
157      * and is equal to (at least one) element of the array.
158      *
159      * @param array the array that may contain the object.
160      * @param o     the object to check the existence of.
161      */
162     public static boolean contains(Object   array[], Object   o)
163     {
164         if (o == null) return false;
165         for (int i = 0; i < array.length; i++)
166             if (o.equals(array[i])) return true;
167         return false;
168     }
169 
170     /**
171      * Prints an array, using 'toString()' on each component.
172      */
173 
174     public static void print(Object   array[])
175     {
176         for (int i = 0; i < array.length; i++)
177             System.out.println(i + ": " + array[i].toString());
178     }
179 
180 
181     public static Object  [] enumerationToArray(Enumeration   e)
182     {
183         Vector   v = new Vector  ();
184         while (e.hasMoreElements()) v.add(e.nextElement());
185         return v.toArray();
186     }
187 
188     public static Enumeration   arrayToEnumeration(Object  [] o)
189     {
190         Vector   v = new Vector  (o.length);
191         for (int i = 0; i < o.length; i++) v.add(o[i]);
192         return v.elements();
193     }
194 
195     public static Object  [] trimNulls(Object  [] o)
196     {
197         Vector   v = new Vector  (o.length);
198         for (int i = 0; i < o.length; i++)
199             if (o[i] != null)
200                 v.add(o[i]);
201         return v.toArray();
202     }
203 }
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