set.java

JAVA在编译原理上的应用。

package lolo.scans;

/** A recognizer class to scan for a character from a set of characters. 
 *
 * @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 Set extends Scan {
    /** The set of characters. */
    protected final String set;
    /** Marks if the symbol character has to be inside or outside <tt>set</tt>. */
    protected final boolean inside;
    /** Just calls <tt>this(set, true)</tt>.
     *
     * @param set the set of characters.
     * @throws IllegalArgumentException is <tt>set</tt> is <tt>null</tt>.
     */
    public Set(String set) throws IllegalArgumentException {
        this(set, true);
    }
    /** Constructs a recognizer which scans one character from a set of characters.
     * If <tt>inside</tt> is <tt>true</tt> the character has to be inside <tt>set</tt>,
     * else outside <tt>set</tt>.
     *
     * @param set the set of characters.
     * @param inside marks if the scanned character has to be inside or outside <tt>set</tt>.
     * @throws IllegalArgumentException if <tt>set</tt> is <tt>null</tt>.
     */
    public Set(String set, boolean inside) throws IllegalArgumentException {
        if (set == null)
            throw new IllegalArgumentException("set == null");
        this.set = set;
        this.inside = inside;
    }
    
    public void reset() {}

    public State nextChar(char ch) {
        return stateObject.set(
            false,                      // more characters ?
            inside ?                    // found symbol ?
                set.indexOf(ch) >= 0 :
                set.indexOf(ch) < 0
        );
    }
    /** Indicates whether some other object is &quot;equal to&quot; this one.
     * 
     * @return <tt>true</tt> the argument is a <tt>Set</tt> and contains the same set,
     * <tt>false</tt> otherwise.
     */
    public boolean equals(Object o) {
        if (o == null || !(o instanceof Set)) return false;
        Set s = (Set) o;
        return this == s || (set.equals(s.set) && inside == s.inside);
    }
    /** Returns a hash code value for this object.
     *
     * @return a hash code value for this object.
     */
    public int hashCode() {
        return set.hashCode();
    }
    
    /** Returns a string representation of the object.
     *
     * @return a string representation of the object.
     */
    public String toString() {
        return getClass().getName()+"["+set+","+inside+"]";
    }
}