001    /*
002     * Copyright 2005 Stephen J. McConnell.
003     *
004     * Licensed  under the  Apache License,  Version 2.0  (the "License");
005     * you may not use  this file  except in  compliance with the License.
006     * You may obtain a copy of the License at
007     *
008     *   http://www.apache.org/licenses/LICENSE-2.0
009     *
010     * Unless required by applicable law or agreed to in writing, software
011     * distributed  under the  License is distributed on an "AS IS" BASIS,
012     * WITHOUT  WARRANTIES OR CONDITIONS  OF ANY KIND, either  express  or
013     * implied.
014     *
015     * See the License for the specific language governing permissions and
016     * limitations under the License.
017     */
018    
019    package net.dpml.state;
020    
021    import java.io.Serializable;
022    
023    /**
024     * Null state implementation.
025     *
026     * @author <a href="http://www.dpml.net">Digital Product Meta Library</a>
027     * @version 1.0.2
028     */
029    public final class NullState implements State, Serializable
030    {   
031       /**
032        * Return the name of the state.
033        * @return the state name
034        */
035        public String getName()
036        {
037            return "";
038        }
039        
040       /**
041        * Set the parent state. 
042        * @param state the parent state
043        */
044        public void setParent( State state )
045        {
046        }
047    
048       /**
049        * Return the parent state to this state or null if this is 
050        * the root of a state graph.
051        * @return the parent state
052        */
053        public State getParent()
054        {
055            return null;
056        }
057        
058       /**
059        * Return the state path.  The path is composed of a sequence of 
060        * states from the root to this state.
061        * @return the state path
062        */
063        public State[] getStatePath()
064        {
065            return new State[0];
066        }
067        
068       /**
069        * Return the substates within this state.
070        * @return the substate array
071        */
072        public State[] getStates()
073        {
074            return new State[0];
075        }
076        
077       /**
078        * Return the array of triggers associated with the state.
079        * @return the trigger array
080        */
081        public Trigger[] getTriggers()
082        {
083            return new Trigger[0];
084        }
085        
086       /**
087        * Return the array of transtions associated with the state.
088        * @return the transition array
089        */
090        public Transition[] getTransitions()
091        {
092            return new Transition[0];
093        }
094        
095       /**
096        * Return the array of operations associated with the state.
097        * @return the operation array
098        */
099        public Operation[] getOperations()
100        {
101            return new Operation[0];
102        }
103        
104       /**
105        * Return the array of operations associated with the state.
106        * @return the operation array
107        */
108        public Interface[] getInterfaces()
109        {
110            return new Interface[0];
111        }
112        
113       /**
114        * Test is the state is a terminal state.
115        * @return true if terminal
116        */
117        public boolean isTerminal()
118        {
119            return false;
120        }
121        
122       /**
123        * Test is this state is equal to the supplied object.
124        * @param other the other object
125        * @return true if equal
126        */
127        public boolean equals( Object other )
128        {
129            if( null == other )
130            {
131                return false;
132            }
133            else
134            {
135                return ( other instanceof NullState );
136            }
137        }
138        
139       /**
140        * Calcualte the hashcode for this instance.
141        * @return the hashcode value
142        */
143        public int hashCode()
144        {
145            return getClass().hashCode();
146        }
147    }