View Javadoc

1   /**
2    *  Copyright 2003-2006 Greg Luck
3    *
4    *  Licensed under the Apache License, Version 2.0 (the "License");
5    *  you may not use this file except in compliance with the License.
6    *  You may obtain a copy of the License at
7    *
8    *      http://www.apache.org/licenses/LICENSE-2.0
9    *
10   *  Unless required by applicable law or agreed to in writing, software
11   *  distributed under the License is distributed on an "AS IS" BASIS,
12   *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   *  See the License for the specific language governing permissions and
14   *  limitations under the License.
15   */
16  
17  package net.sf.ehcache;
18  
19  import java.io.Serializable;
20  
21  /**
22   * A pre JDK1.5 compatible enum class to indicate the status of a {@link CacheManager} or {@link Cache}.
23   * <p/>
24   * ehcache historically used int values for status. This is unsuitable for third party use thus this class.
25   * Methods are provided to convert from the int status values to enum values and vice versa.
26   *
27   * @author Greg Luck
28   * @version $Id: Status.java 52 2006-04-24 14:50:03Z gregluck $
29   * @since 1.2
30   * @noinspection SerializableHasSerializationMethods
31   */
32  public final class Status implements Serializable {
33      /**
34       * The cache is uninitialised. It cannot be used.
35       */
36      public static final Status STATUS_UNINITIALISED = new Status(0, "STATUS_UNINITIALISED");
37      /**
38       * The cache is alive. It can be used.
39       */
40      public static final Status STATUS_ALIVE = new Status(1, "STATUS_ALIVE");
41      /**
42       * The cache is shudown. It cannot be used.
43       */
44      public static final Status STATUS_SHUTDOWN = new Status(2, "STATUS_SHUTDOWN");
45  
46      private static final long serialVersionUID = 2732730630423367732L;
47  
48      private static final Status[] STATUSES = {STATUS_UNINITIALISED, STATUS_ALIVE, STATUS_SHUTDOWN};
49  
50      private final String name;
51      private final int intValue;
52  
53      private Status(int intValue, String name) {
54          this.intValue = intValue;
55          this.name = name;
56  
57      }
58  
59      /**
60       * Returns a string representation of the object. In general, the
61       * <code>toString</code> method returns a string that
62       * "textually represents" this object. The result should
63       * be a concise but informative representation that is easy for a
64       * person to read.
65       * It is recommended that all subclasses override this method.
66       * <p/>
67       * The <code>toString</code> method for class <code>Object</code>
68       * returns a string consisting of the name of the class of which the
69       * object is an instance, the at-sign character `<code>@</code>', and
70       * the unsigned hexadecimal representation of the hash code of the
71       * object. In other words, this method returns a string equal to the
72       * value of:
73       * <blockquote>
74       * <pre>
75       * getClass().getName() + '@' + Integer.toHexString(hashCode())
76       * </pre></blockquote>
77       *
78       * @return a string representation of the object.
79       */
80      public String toString() {
81          return name;
82      }
83  
84      /**
85       * @param statusAsInt an int argument between 1 and 3.
86       * @return an enum Status
87       * @throws IllegalArgumentException if the argument is not between 1 and 3
88       */
89      public static Status convertIntToStatus(int statusAsInt) throws IllegalArgumentException {
90          if ((statusAsInt < STATUS_UNINITIALISED.intValue) || (statusAsInt > STATUS_SHUTDOWN.intValue)) {
91              throw new IllegalArgumentException("int value of statuses must be between 1 and three");
92          }
93          return STATUSES[statusAsInt];
94      }
95  
96      /**
97       * Returns the int value of status, for backward compatibility with ehcache versions below 1.2
98       * @return the int value of this status.
99       */
100     public int intValue() {
101         return intValue;
102     }
103 
104     /**
105      * Indicates whether some other object is "equal to" this one.
106      * <p/>
107      * The <code>equals</code> method implements an equivalence relation
108      * on non-null object references:
109      * <ul>
110      * <li>It is <i>reflexive</i>: for any non-null reference value
111      * <code>x</code>, <code>x.equals(x)</code> should return
112      * <code>true</code>.
113      * <li>It is <i>symmetric</i>: for any non-null reference values
114      * <code>x</code> and <code>y</code>, <code>x.equals(y)</code>
115      * should return <code>true</code> if and only if
116      * <code>y.equals(x)</code> returns <code>true</code>.
117      * <li>It is <i>transitive</i>: for any non-null reference values
118      * <code>x</code>, <code>y</code>, and <code>z</code>, if
119      * <code>x.equals(y)</code> returns <code>true</code> and
120      * <code>y.equals(z)</code> returns <code>true</code>, then
121      * <code>x.equals(z)</code> should return <code>true</code>.
122      * <li>It is <i>consistent</i>: for any non-null reference values
123      * <code>x</code> and <code>y</code>, multiple invocations of
124      * <tt>x.equals(y)</tt> consistently return <code>true</code>
125      * or consistently return <code>false</code>, provided no
126      * information used in <code>equals</code> comparisons on the
127      * objects is modified.
128      * <li>For any non-null reference value <code>x</code>,
129      * <code>x.equals(null)</code> should return <code>false</code>.
130      * </ul>
131      * <p/>
132      * The <tt>equals</tt> method for class <code>Object</code> implements
133      * the most discriminating possible equivalence relation on objects;
134      * that is, for any non-null reference values <code>x</code> and
135      * <code>y</code>, this method returns <code>true</code> if and only
136      * if <code>x</code> and <code>y</code> refer to the same object
137      * (<code>x == y</code> has the value <code>true</code>).
138      * <p/>
139      * Note that it is generally necessary to override the <tt>hashCode</tt>
140      * method whenever this method is overridden, so as to maintain the
141      * general contract for the <tt>hashCode</tt> method, which states
142      * that equal objects must have equal hash codes.
143      *
144      * @param object the reference object with which to compare.
145      * @return <code>true</code> if this object is the same as the obj
146      *         argument; <code>false</code> otherwise.
147      * @see #hashCode()
148      * @see java.util.Hashtable
149      */
150     public boolean equals(Object object) {
151         if (!(object instanceof Status)) {
152             return false;
153         }
154         return ((Status) object).intValue == intValue;
155     }
156 
157     /**
158      * Equality checker when the comparison object is of the same type.
159      * @param status the status to check
160      * @return true is the statuses are the same
161      */
162     public boolean equals(Status status) {
163         return intValue == status.intValue;
164     }
165 
166     /**
167      * Returns a hash code value for the object. This method is
168      * supported for the benefit of hashtables such as those provided by
169      * <code>java.util.Hashtable</code>.
170      * <p/>
171      * The general contract of <code>hashCode</code> is:
172      * <ul>
173      * <li>Whenever it is invoked on the same object more than once during
174      * an execution of a Java application, the <tt>hashCode</tt> method
175      * must consistently return the same integer, provided no information
176      * used in <tt>equals</tt> comparisons on the object is modified.
177      * This integer need not remain consistent from one execution of an
178      * application to another execution of the same application.
179      * <li>If two objects are equal according to the <tt>equals(Object)</tt>
180      * method, then calling the <code>hashCode</code> method on each of
181      * the two objects must produce the same integer result.
182      * <li>It is <em>not</em> required that if two objects are unequal
183      * according to the {@link Object#equals(Object)}
184      * method, then calling the <tt>hashCode</tt> method on each of the
185      * two objects must produce distinct integer results.  However, the
186      * programmer should be aware that producing distinct integer results
187      * for unequal objects may improve the performance of hashtables.
188      * </ul>
189      * <p/>
190      * As much as is reasonably practical, the hashCode method defined by
191      * class <tt>Object</tt> does return distinct integers for distinct
192      * objects. (This is typically implemented by converting the internal
193      * address of the object into an integer, but this implementation
194      * technique is not required by the
195      * Java<font size="-2"><sup>TM</sup></font> programming language.)
196      *
197      * @return a hash code value for this object.
198      * @see Object#equals(Object)
199      * @see java.util.Hashtable
200      */
201     public int hashCode() {
202         return intValue;
203     }
204 
205 }