Java/Collections Data Structure/State Machine
The representation of a finite state machine
/*
* JBoss, Home of Professional Open Source
* Copyright 2005, JBoss Inc., and individual contributors as indicated
* by the @authors tag. See the copyright.txt in the distribution for a
* full listing of individual contributors.
*
* This is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* This software is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this software; if not, write to the Free
* Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA, or see the FSF site: http://www.fsf.org.
*/
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
/**
* The representation of a finite state machine.
*
* @author Scott.Stark@jboss.org
* @version $Revision: 2787 $
*/
@SuppressWarnings("unchecked")
public class StateMachine implements Cloneable {
/** A description of the state machine */
private String description;
/** The set of states making up the state machine */
private HashSet states;
/** The starting state */
private State startState;
/** The current state of the state machine */
private State currentState;
/**
* Create a state machine given its states and start state.
*
* @param states -
* Set<State> for the state machine
* @param startState -
* the starting state
*/
public StateMachine(Set states, State startState) {
this(states, startState, null);
}
/**
* Create a state machine given its states and start state.
*
* @param states -
* Set<State> for the state machine
* @param startState -
* the starting state
* @param description -
* an optional description of the state machine
*/
public StateMachine(Set states, State startState, String description) {
this.states = new HashSet(states);
this.startState = startState;
this.currentState = startState;
this.description = description;
}
/**
* Make a copy of the StateMachine maintaining the current state.
*
* @return a copy of the StateMachine.
*/
public Object clone() {
StateMachine clone = new StateMachine(states, startState, description);
clone.currentState = currentState;
return clone;
}
/**
* Get the state machine description.
*
* @return an possibly null description.
*/
public String getDescription() {
return description;
}
/**
* Get the current state of the state machine.
*
* @return the current state.
*/
public State getCurrentState() {
return currentState;
}
/**
* Get the start state of the state machine.
*
* @return the start state.
*/
public State getStartState() {
return startState;
}
/**
* Get the states of the state machine.
*
* @return the machine states.
*/
public Set getStates() {
return states;
}
/**
* Transition to the next state given the name of a valid transition.
*
* @param actionName -
* the name of transition that is valid for the current state.
* @return the next state
* @throws IllegalTransitionException
*/
public State nextState(String actionName) throws IllegalTransitionException {
Transition t = currentState.getTransition(actionName);
if (t == null) {
String msg = "No transition for action: "" + actionName + "" from state: ""
+ currentState.getName() + """;
throw new IllegalTransitionException(msg);
}
State nextState = t.getTarget();
System.out.println("nextState(" + actionName + ") = " + nextState);
currentState = nextState;
return currentState;
}
/**
* Reset the state machine back to the start state
*
* @return the start state
*/
public State reset() {
this.currentState = startState;
return currentState;
}
public String toString() {
StringBuffer tmp = new StringBuffer("StateMachine[:\n");
tmp.append("\tCurrentState: " + currentState.getName());
Iterator i = states.iterator();
while (i.hasNext()) {
tmp.append("\n").append(i.next());
}
tmp.append("]");
return tmp.toString();
}
}
/*
* JBoss, Home of Professional Open Source Copyright 2005, JBoss Inc., and
* individual contributors as indicated by the @authors tag. See the
* copyright.txt in the distribution for a full listing of individual
* contributors.
*
* This is free software; you can redistribute it and/or modify it under the
* terms of the GNU Lesser General Public License as published by the Free
* Software Foundation; either version 2.1 of the License, or (at your option)
* any later version.
*
* This software is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
* FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
* details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this software; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA, or see the FSF
* site: http://www.fsf.org.
*/
/**
* The respresentation of a state in a state machine.
*
* @author Scott.Stark@jboss.org
* @version $Revision: 2787 $
*/
@SuppressWarnings("unchecked")
class State {
/** The name of the state */
private String name;
/** HashMap<String, Transition> */
private HashMap allowedTransitions = new HashMap();
/** Arbitrary state data */
private Object data;
public State(String name) {
this(name, null);
}
public State(String name, Map transitions) {
this.name = name;
if (transitions != null) {
allowedTransitions.putAll(transitions);
}
}
/**
* Get the state name.
*
* @return the name of the state.
*/
public String getName() {
return name;
}
public Object getData() {
return data;
}
public void setData(Object data) {
this.data = data;
}
/**
* An accept state is indicated by no transitions
*
* @return true if this is an accept state, false otherwise.
*/
public boolean isAcceptState() {
return allowedTransitions.size() == 0;
}
/**
* Add a transition to the allowed transition map.
*
* @param transition
* @return this to allow chained addTransition calls
*/
public State addTransition(Transition transition) {
allowedTransitions.put(transition.getName(), transition);
return this;
}
/**
* Lookup an allowed transition given its name.
*
* @param name -
* the name of a valid transition from this state.
* @return the valid transition if it exists, null otherwise.
*/
public Transition getTransition(String name) {
Transition t = (Transition) allowedTransitions.get(name);
return t;
}
/**
* Get the Map<String, Transition> of allowed transitions for this state.
*
* @return the allowed transitions map.
*/
public Map getTransitions() {
return allowedTransitions;
}
public String toString() {
StringBuffer tmp = new StringBuffer("State(name=");
tmp.append(name);
Iterator i = allowedTransitions.entrySet().iterator();
while (i.hasNext()) {
Map.Entry e = (Map.Entry) i.next();
tmp.append("\n\t on: ");
tmp.append(e.getKey());
Transition t = (Transition) e.getValue();
tmp.append(" go to: ");
tmp.append(t.getTarget().getName());
}
tmp.append(")");
return tmp.toString();
}
}
/*
* JBoss, Home of Professional Open Source Copyright 2005, JBoss Inc., and
* individual contributors as indicated by the @authors tag. See the
* copyright.txt in the distribution for a full listing of individual
* contributors.
*
* This is free software; you can redistribute it and/or modify it under the
* terms of the GNU Lesser General Public License as published by the Free
* Software Foundation; either version 2.1 of the License, or (at your option)
* any later version.
*
* This software is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
* FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
* details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this software; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA, or see the FSF
* site: http://www.fsf.org.
*/
/**
* A representation of a transition from a state to another state.
*
* @author Scott.Stark@jboss.org
* @version $Revision: 1958 $
*/
class Transition {
private String name;
private State target;
public Transition(String name, State target) {
this.name = name;
this.target = target;
}
public String getName() {
return name;
}
public State getTarget() {
return target;
}
}
/*
* JBoss, Home of Professional Open Source Copyright 2005, JBoss Inc., and
* individual contributors as indicated by the @authors tag. See the
* copyright.txt in the distribution for a full listing of individual
* contributors.
*
* This is free software; you can redistribute it and/or modify it under the
* terms of the GNU Lesser General Public License as published by the Free
* Software Foundation; either version 2.1 of the License, or (at your option)
* any later version.
*
* This software is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
* FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
* details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this software; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA, or see the FSF
* site: http://www.fsf.org.
*/
/**
* An exception thrown when an invalid transition is attempted from a state.
*
* @author Scott.Stark@jboss.org
* @version $Revision: 2800 $
*/
class IllegalTransitionException extends Exception {
/** The serialVersionUID */
private static final long serialVersionUID = -3392564168782896452L;
public IllegalTransitionException(String msg) {
super(msg);
}
}
