word.java

JAVA在编译原理上的应用。

package lolo.scans;

/** A recognizer class to scan for a string (a word). 
 *
 * @author <a href="http://www.inf.uos.de/bernd" target="_blank">Bernd K&uuml;hl</a>
           (<a href="mailto:[e-mail]">[e-mail]</a>)
 */
public class Word extends Scan {
    /** The word. */
    protected final char[] word;
    /** Marks the next character inside <tt>word</tt> to find. */
	protected transient int index;
    private int hashCode;
    
    /** Constructs an instance scanning the string <tt>word</tt>.
     *
     * @param word the string to search.
     * @throws IllegalArgumentException if <tt>word</tt> is <tt>null</tt> or contains no character.
     */
	public Word(String word) throws IllegalArgumentException {
        if (word == null)
            throw new IllegalArgumentException("null word");
        if (word.length() == 0)
            throw new IllegalArgumentException("word.length() == 0");
        this.word = word.toCharArray();
        this.hashCode = word.hashCode();
	}
        
	public void reset() {
        index = 0;
	}
        
	public State nextChar(char ch) {
        boolean okay = ch == word[index++];
        return stateObject.set(
            okay && index < word.length,	// more
            okay && index == word.length	// found
        );
	}
    
    /** Returns a string representation of the object.
     *
     * @return a string representation of the object.
     */
	public String toString() {
        return super.toString()+"["+new String(word)+"]";
	}   
    /** Returns a hash code value for this object.
     *
     * @return a hash code value for this object.
     */
    public int hashCode() {
        return hashCode;
    }
    /** Compares the receiver to the specified object. The result is <tt>true</tt> if and only if
     * the argument is not <tt>null</tt> and is a <tt>Word</tt> object that represents the String 
     * as this object..
     *
     * @return Compares the receiver to the specified object. The result is <tt>true</tt> if and only if
     * the argument is not <tt>null</tt> and is a <tt>Word</tt> object that represents the String 
     * as this object..
     */
    public boolean equals(Object o) {
        if (o == null || !(o instanceof Word)) return false;
        if (o == this) return true;
        
        final int length = word.length;
        for (int i = 0; i < length; i++)
            if (word[i] != ((Word) o).word[i])
                return false;
        return true;
    }
}