Java code Regular Expression to NFA (Pease do not just paste somthing you found on github that is not helpful)

Class NFAState

java.lang.Object

fa.State

fa.nfa.NFAState

public class NFAState extends State

Constructor Summary

Constructor and Description

NFAState(java.lang.String name)

Method Summary

Methods

Modifier and Type	Method and Description
void	addTransition(char c, NFAState to)
java.lang.String	getTransitions()
boolean	isFinal()
void	setFinal() Sets this state as a final
void	setNonFinal() Sets this state as non-final
java.util.Set	toStates(char c)
java.lang.String	toString()

Methods inherited from class fa.State

getName

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

NFAState

public NFAState(java.lang.String name)

Method Detail

setFinal

public void setFinal()

Sets this state as a final

isFinal

public boolean isFinal()

addTransition

public void addTransition(char c, NFAState to)

toStates

public java.util.Set toStates(char c)

toString

public java.lang.String toString()

Overrides:

toString in class State

setNonFinal

public void setNonFinal()

Sets this state as non-final

getTransitions

public java.lang.String getTransitions()

Class NFA

java.lang.Object

fa.nfa.NFA

All Implemented Interfaces:

FAInterface, NFAInterface

public class NFA extends java.lang.Object implements FAInterface, NFAInterface

Constructor Summary

Constructor and Description

NFA()

Method Summary

Methods

Modifier and Type	Method and Description
void	addAbc(java.util.Set moreAbc) Adds a set of symbols to its alphabet.
void	addFinalState(java.lang.String finalSateName) Creates a new final state with finalSateName label if no state with such label exists.
void	addNFAStates(java.util.Set addStates) Adds a set of NFA states to this NFA.
void	addStartState(java.lang.String startStateName) Creates a new start state with startStateName label if no state with such label exists.
void	addState(java.lang.String stateName) Creates a new regular state with stateSTate label if no state with such label exists.
void	addTransition(java.lang.String fromName, char c, java.lang.String toName) Creates a transition from fromName state to toName state on symbol c
java.util.Set	eClosure(NFAState s) Does all epsilon transitions and determine what states can be reached from s
java.util.Set	getABC() Getter for Sigma
DFA	getDFA()
java.util.Set	getFinalStates() Getter for F
State	getStartState() Getter for q0
java.util.Set	getStates() Returns the set of states of this NFA
java.util.Set	getToState(NFAState from, char onSymb) Return delta entries
java.lang.String	toString()

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

NFA

public NFA()

Method Detail

addFinalState

public void addFinalState(java.lang.String finalSateName)

Creates a new final state with finalSateName label if no state with such label exists. Otherwise it finds an NFA state with such label and set it to final.

Specified by:

addFinalState in interface FAInterface

Parameters:

finalSateName - - the label of a new finals state

addStartState

public void addStartState(java.lang.String startStateName)

Creates a new start state with startStateName label if no state with such label exists. Otherwise it finds an NFA state with such label and set it to start state.

Specified by:

addStartState in interface FAInterface

Parameters:

startStateName - - the label of a new finals state

addState

public void addState(java.lang.String stateName)

Creates a new regular state with stateSTate label if no state with such label exists. Otherwise it finds an NFA state with such label and set it to start state.

Specified by:

addState in interface FAInterface

Parameters:

startStateName - - the label of a new finals state

addTransition

public void addTransition(java.lang.String fromName, char c, java.lang.String toName)

Creates a transition from fromName state to toName state on symbol c

Specified by:

addTransition in interface FAInterface

Parameters:

fromName - - the label of the from state

c - - the symbol of the transtion

toName - - the label of the to state

getStartState

public State getStartState()

Description copied from interface: FAInterface

Getter for q0

Specified by:

getStartState in interface FAInterface

Returns:

the start state of FA

getFinalStates

public java.util.Set getFinalStates()

Description copied from interface: FAInterface

Getter for F

Specified by:

getFinalStates in interface FAInterface

Returns:

a set of final states that FA has

getDFA

public DFA getDFA()

Specified by:

getDFA in interface NFAInterface

Returns:

equivalent DFA

eClosure

public java.util.Set eClosure(NFAState s)

Does all epsilon transitions and determine what states can be reached from s

Specified by:

eClosure in interface NFAInterface

Parameters:

s -

Returns:

set of states that can be reached from s on epsilon trans.

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

addNFAStates

public void addNFAStates(java.util.Set addStates)

Adds a set of NFA states to this NFA. If a state is not NFA state then the method will throw an exception.

Parameters:

addStates - - the set of NFA states to be added

addAbc

public void addAbc(java.util.Set moreAbc)

Adds a set of symbols to its alphabet.

Parameters:

moreAbc - - set of symbols to be added.

getStates

public java.util.Set getStates()

Returns the set of states of this NFA

Specified by:

getStates in interface FAInterface

Returns:

set of states

getToState

public java.util.Set getToState(NFAState from, char onSymb)

Description copied from interface: NFAInterface

Return delta entries

Specified by:

getToState in interface NFAInterface

Parameters:

from - - the source state

onSymb - - the label of the transition

Returns:

a set of sink states

getABC

public java.util.Set getABC()

Description copied from interface: FAInterface

Getter for Sigma

Specified by:

getABC in interface FAInterface

Returns:

the alphabet of FA

Here is the code I have so far:

public class RE implements REInterface {

private NFA nfa = null;

private String regEx;

public RE(String regEx) {

this.regEx = regEx ;

}

@Override

public NFA getNFA() {

nfa = regex();

return nfa;

}

/* Recursive descent parsing internals. */

/**

* returns the next item of input without consuming it

*/

private char peek() {

return regEx.charAt(0) ;

}

/**

* consumes the next item of input, failing if not equal to item.

*/

private void eat(char c) {

if (peek() == c)

this.regEx = this.regEx.substring(1) ;

else

throw new

RuntimeException("Expected: " + c + "; got: " + peek()) ;

}

/**

* returns the next item of input and consumes it

*/

private char next() {

char c = peek() ;

eat(c) ;

return c ;

}

private boolean more() {

return regEx.length() > 0 ;

}

/* Regular expression term types. */

/**

* must parse at least one term,

* and whether we parse another

* depends only on what we find

* afterward

*

* @return NFA

*/

private NFA regex() {

NFA term = term();

if (more() && peek() == '|') {

eat('|');

NFA regex = regex();

return regex; //return new Choice(term,regex) ;

} else {

return term;

}

}

/**

* check that it has not reached the boundary

* of a term or the end of the input

* @return NFA

*/

private NFA term() {

NFA factor = null; //NFA.blank???

while (more() && peek() != ')' && peek() != '|') {

NFA nextFactor = factor() ;

factor = nextFactor; //factor = new Sequence(factor,nextFactor) ;

}

return factor;

}

/**

* parse a base and then any number of Kleene stars

* @return NFA

*/

private NFA factor() {

NFA baseNFA = base() ;

while (more() && peek() == '*') {

eat('*') ;

//base = new Repetition(base) ;

}

return baseNFA ;

}

/**

* checks to see which of the three cases it has encountered

* @return NFA

*/

private NFA base() {

switch (peek()) {

case '(':

eat('(') ;

NFA r = regex() ;

eat(')') ;

return r ;

default:

return new Primitive(next());

}

}

}