simpleidentifier.java

JAVA在编译原理上的应用。

package lolo.scans;

/** Instances of this class scan for <tt>[_a-zA-Z][_a-zA-Z0-9]*</tt>.
 *
 * @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 SimpleIdentifier extends Scan {
    /** Marks if the first character is checked. */
    protected transient boolean start = true;
    
    public void reset() {
        start = true;
    }
    
    /** Tests the first character.
     *
     * @return <tt>true</tt> if the character is a legal first character.
     * @param ch the first charatcer of the symbol.
     */
    protected boolean testStart(char ch) {
        return ch == '_' || (ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z' );
    }
    
    /** Tests the characters.
     * @return <tt>true</tt> if the characters are a legal characters.
     * @param ch the next charatcer of the symbol.
     */
    protected boolean testPart(char ch) {
        return ch == '_' || (ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z' ) || (ch >= '0' && ch <= '9' );
    }
    
    public State nextChar(char ch) {
        boolean b = start? testStart(ch) : testPart(ch);
        start = false;
        return stateObject.set (
            b,	// more
            b	// found
        );
    }
}