scanstring.java

java 作图的程序

package graph;

import java.awt.*;
import java.applet.*;
import java.util.*;
import java.lang.*;
/*
************************************************************************
**
**    Class  ScanString
**
**************************************************************************
**    Copyright (C) 1996 Leigh Brookshaw
**
**    This program is free software; you can redistribute it and/or modify
**    it under the terms of the GNU General Public License as published by
**    the Free Software Foundation; either version 2 of the License, or
**    (at your option) any later version.
**
**    This program 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 General Public License for more details.
**
**    You should have received a copy of the GNU General Public License
**    along with this program; if not, write to the Free Software
**    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
**************************************************************************/

/**
 * This class is similar to the ScanWord class, except it scans a string
 * for keywords rather than an input stream.
 *
 * @version $Revision: 1.5 $, $Date: 1996/07/12 00:35:49 $
 * @author Leigh Brookshaw
 */ 

public class ScanString extends Object {
/*
*********************
** Constants
********************/
  /**
   * flag an unknown token
   */
     public final static int UNKNOWN = -256;
  /**
   * Flag an error
   */
     public final static int ERROR   = -257;
  /**
   * Flag a Number
   */
     public final static int NUMBER  = -258;
  /**
   * flag the End of String
   */
     public final static int EOS     = -259;
     
/*
**********************
** Private Variables
********************/

     private String string;
     
     private char buffer[];
     
     private int count;
     private int position;
     private int kwlength;
     
     public String sval;
     public double nval;
     
/*
**   The hash table containing the keyword/value pairs.
*/     
     private Hashtable kwords = new Hashtable();

/*
******************
**
** Constructors
**
*****************/
  /**
   * Instantiate the Class
   */
     public ScanString( ) {
         string = null;
         count = 0;
         position = 0;
         kwlength = 0;
         buffer = new char[32];
         sval = null;
         nval = 0.0;
     }
  /**
   * Instantaite the Class
   * @param s String to scan for tokens
   */
     public ScanString( String s ) {
         setString(s);
     }
     
/*
********************
**
**  Public Methods
**
*******************/

  /**
   * Set the string to be scanned
   * @param s String
   */
    public void setString( String s ) {
         if(s == null) return;
         string = new String(s);
         //System.out.println("ScanSring: string="+string);
     }
         

  /**
   *  Add a keyword/token pair to the table of keywords to scan for.
   * @param s keyword string to scan for
   * @param i token to return when the keyword is found
   */
     public void addKeyWord ( String s, int i) {

          if(s == null) return;

          if( kwlength < s.length() ) kwlength = s.length();
          kwords.put(s.toLowerCase(), new Integer(i));

          //System.out.println("addKeyWord: key="+s.toLowerCase()+" value="+i);

	}
  /**
   * @param s keyword string
   * @return the token corresponding to the keyword
   */
     public int getKeyValue (String s) {


          if(s == null) return UNKNOWN;


          if( !kwords.containsKey(s.toLowerCase())) return UNKNOWN;

          Integer i = (Integer)kwords.get(s.toLowerCase());

          if(i == null) return UNKNOWN;
          else          return i.intValue();
	}
  /**
   *   Clear the table containing the keyword/token pairs
   */
     public void resetKeyWords () {
          kwords.clear();
          kwlength = 0;
	}
  /**
   *  Process the string and return the next token found.
   * @return token found
   */
     public int nextWord() {
        int i;
     	char c;
        int word;
        int count = 0;
        char buffer[] = new char[string.length()];
        boolean exponent = false;
        boolean point = false;


        if(position >= string.length() ) return EOS;

        c = string.charAt(position);
/*
**      Remove white space
*/
        while( c == 32 || c == 9 || c == 10 || c == 11 || c == 13 ) {
                position++;
                if( position >= string.length() ) return EOS;
                c = string.charAt(position);
	}
/*
**      Is this the start of a number ?
*/

        if( (c >= '0' && c <= '9') || c == '.' ) {

               //System.out.println("ScanString: Scan for number!");

               for(i=position; i<string.length(); i++) {
                   c = string.charAt(i);

                   if(exponent && ( c < '0' || c > '9' ) ) break;

                   if( c == 'E' || c =='e' ||
                       c == 'D' || c =='d' ) {
                             exponent = true;
                             buffer[count++] = 'e';

                             c = string.charAt(i+1);
                             if(  c == '-' || c == '+' ) {
                                     buffer[count++] = c;
                                     i++;
                             }
                   } else
                   if( point && c == '.' ) {
                                   break;
                   } else
	           if( c == '.' ) {
                                   point = true;
                                   buffer[count++] = c; 
                   } else
                   if(  c < '0' || c > '9' ) {
                                  break;
                   } else {
                                  buffer[count++] = c;
                   }
	       }

 
              try {
               sval = new String(buffer,0,count);
               nval = Double.valueOf(sval).doubleValue();
               position += count;
               return NUMBER;
	       }
               catch (Exception e) {
               return ERROR;
	       }

        } else {
/*
**      Scan for a keyword
*/
         //System.out.println("ScanString: Scan for Word!");
         //System.out.println("ScanString: Maximum Keyword length "+kwlength);

           int last = UNKNOWN;
           int nchar = 0;
           int pos = position;
           
           while (pos < string.length() )  {

        	buffer[count++] = string.charAt(pos++);

                word = getKeyValue(new String(buffer,0,count));

                if(word != UNKNOWN ) {
                      last = word;
                      nchar = count;
                    //System.out.println("ScanString: Found KeyWord - "+
                    //       new String(buffer,0,count));
                } else
	        if( nchar == 0 && count >= kwlength ) {
                      return ERROR;
                } else
                if( count >= kwlength ) {
                       sval = new String(buffer,0,nchar);
                       position += nchar;
                     //System.out.println("ScanString: Returning KeyWord - "+
                     //         sval);
                       return last;
	        }
           }

           if( nchar != 0 ) {
               sval = new String(buffer,0,nchar);
               position += nchar;
             //System.out.println("ScanString: Returning KeyWord - "+
             //                 sval);
               return last;
	   }


	}    
        return ERROR;
        
        
        
     }
     
     

   }