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 1.0.4 028 */ 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 }