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    • net.automatalib.words.EmptyWord Maven / Gradle / Ivy

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    This artifact contains the API of AutomataLib, which mainly consists of interfaces for the various concepts and automaton models supported by the AutomataLib core. In addition to that, it also defines some fundamental classes for dealing with words of symbols.

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    /* Copyright (C) 2013 TU Dortmund
 * This file is part of AutomataLib, http://www.automatalib.net/.
 * 
 * AutomataLib is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License version 3.0 as published by the Free Software Foundation.
 * 
 * AutomataLib 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 AutomataLib; if not, see
 * http://www.gnu.de/documents/lgpl.en.html.
 */
package net.automatalib.words;

import java.util.Collections;
import java.util.List;
import java.util.NoSuchElementException;

/**
 * The empty word.
 * 
 * This class has no type parameter, as there are no non-null instances
 * of the symbol class involved. Hence, Java's generic mechanism allows to maintain
 * only a single instance of this class. 
 * 
 * @author Malte Isberner 
 *
 * @see Collections#emptyList()
 */
final class EmptyWord extends Word {
	
	public static final EmptyWord INSTANCE
		= new EmptyWord();
	
	/*
	 * (non-Javadoc)
	 * @see net.automatalib.words.Word#getSymbol(int)
	 */
	@Override
	public Object getSymbol(int index) {
		return null;
	}

	/*
	 * (non-Javadoc)
	 * @see net.automatalib.words.Word#length()
	 */
	@Override
	public int length() {
		return 0;
	}
	

	/*
	 * (non-Javadoc)
	 * @see net.automatalib.words.Word#subWord(int, int)
	 */
	@Override
	public Word _subWord(int fromIndex, int toIndex) {
		return this;
	}

	/*
	 * (non-Javadoc)
	 * @see net.automatalib.words.Word#writeToArray(int, java.lang.Object[], int, int)
	 */
	@Override
	public void writeToArray(int offset, Object[] array, int tgtOffset,
			int length) {
	}

	/*
	 * (non-Javadoc)
	 * @see net.automatalib.words.Word#asList()
	 */
	@Override
	public List asList() {
		return Collections.emptyList();
	}

	/*
	 * (non-Javadoc)
	 * @see net.automatalib.words.Word#canonicalNext(net.automatalib.words.Alphabet)
	 */
	@Override
	public Word canonicalNext(Alphabet sigma) {
		return new LetterWord<>(sigma.getSymbol(0));
	}

	/*
	 * (non-Javadoc)
	 * @see net.automatalib.words.Word#append(java.lang.Object)
	 */
	@Override
	public Word append(Object symbol) {
		return new LetterWord<>(symbol);
	}

	/*
	 * (non-Javadoc)
	 * @see net.automatalib.words.Word#prepend(I[])
	 */
	@Override
	public Word prepend(Object symbol) {
		return append(symbol);
	}


	/*
	 * (non-Javadoc)
	 * @see net.automatalib.words.Word#isPrefixOf(net.automatalib.words.Word)
	 */
	@Override
	public boolean isPrefixOf(Word other) {
		return true;
	}

	/*
	 * (non-Javadoc)
	 * @see net.automatalib.words.Word#longestCommonPrefix(net.automatalib.words.Word)
	 */
	@Override
	public Word longestCommonPrefix(Word other) {
		return this;
	}

	/*
	 * (non-Javadoc)
	 * @see net.automatalib.words.Word#isSuffixOf(net.automatalib.words.Word)
	 */
	@Override
	public boolean isSuffixOf(Word other) {
		return true;
	}

	/*
	 * (non-Javadoc)
	 * @see net.automatalib.words.Word#longestCommonSuffix(net.automatalib.words.Word)
	 */
	@Override
	public Word longestCommonSuffix(Word other) {
		return this;
	}
	
	/*
	 * (non-Javadoc)
	 * @see net.automatalib.words.Word#lastSymbol()
	 */
	@Override
	public Object lastSymbol() {
		throw new NoSuchElementException();
	}
	
	/*
	 * (non-Javadoc)
	 * @see net.automatalib.words.Word#flatten()
	 */
	@Override
	public Word flatten() {
		return this;
	}

	/* (non-Javadoc)
	 * @see net.automatalib.words.Word#trimmed()
	 */
	@Override
	public Word trimmed() {
		return this;
	}
	
	
}
    
    
    
    

    




    
    
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