scanner.java

数据挖掘中

          return this.ttype = T_ID;  /* return 'identifier' */

        case S_FRAC:            /* --- number (digit & point read) */
          s.append((char)c);    /* buffer character */
          if  (ccl == C_DIGIT)  /* if another digit follows, */
            break;              /* do nothing else */
          if ((c == 'e')        /* if an exponent indicator follows, */
          ||  (c == 'E')) {     /* (lower- or uppercase), */
            state = S_EXPIND; break; } /* go to exponent state */
          if ((ccl == C_LETTER) /* if a letter */
          ||  (ccl == C_POINT)  /* or a decimal point */
          ||  (ccl == C_SIGN)){ /* or a sign follows, */
            state = S_ID; break;/* go to 'identifier' state */
          }                     /* otherwise */
          this.ungetc(c);       /* put back last character, */
          this.value = s.toString().substring(0,s.length()-1);
          return this.ttype = T_NUM; /* and return 'number' */

        case S_EXPIND:          /* --- exponent (indicator read) */
          s.append((char)c);    /* buffer character */
          if  (ccl == C_SIGN) {        /* if a sign follows, */
            state = S_EXPSGN; break; } /* go to 2nd 'exponent' state */
          if  (ccl == C_DIGIT) {       /* if a digit follows, */
            state = S_EXPDIG; break; } /* go to 3rd 'exponent' state */
          if ((ccl == C_LETTER) /* if a letter */
          ||  (ccl == C_POINT)){/* or a decimal point follows */
            state = S_ID; break;/* go to 'identifier' state */
          }                     /* otherwise */
          this.ungetc(c);       /* put back last character, */
          this.value = s.toString().substring(0,s.length()-1);
          return this.ttype = T_ID;  /* return 'identifier' */

        case S_EXPSGN:          /* --- exponent (sign read) */
          s.append((char)c);    /* buffer character */
          if  (ccl == C_DIGIT) {      /* if a digit follows, */
            state = S_EXPDIG; break;} /* do nothing else */
          if ((ccl == C_LETTER) /* if a letter */
          ||  (ccl == C_POINT)  /* or a decimal point */
          ||  (ccl == C_SIGN)){ /* or a sign follows */
            state = S_ID; break;/* go to 'identifier' state */
          }                     /* otherwise */
          this.ungetc(c);       /* put back last character, */
          this.value = s.toString().substring(0,s.length()-1);
          return this.ttype = T_ID;  /* return 'identifier' */

        case S_EXPDIG:          /* --- exponent (digit read) */
          s.append((char)c);    /* buffer character */
          if  (ccl == C_DIGIT)  /* if another digit follows, */
            break;              /* do nothing else */
          if ((ccl == C_LETTER) /* if a letter */
          ||  (ccl == C_POINT)  /* or a decimal point */
          ||  (ccl == C_SIGN)){ /* or a sign follows, */
            state = S_ID; break;/* go to 'identifier' state */
          }                     /* otherwise */
          this.ungetc(c);       /* put back last character, */
          this.value = s.toString().substring(0,s.length()-1);
          return this.ttype = T_NUM; /* and return 'number' */

        case S_SIGN:            /* --- number (sign read) */
          s.append((char)c);    /* buffer character */
          if  (ccl == C_DIGIT) {       /* if a digit follows, */
            state = S_NUMDIG; break; } /* go to 'number' state */
          if  (ccl == C_POINT) {       /* if a decimal point follows, */
            state = S_NUMPT; break; }  /* go to fraction state */
          if ((ccl == C_LETTER)        /* if a letter */
          ||  (ccl == C_SIGN)) {       /* or a sign follows, */
            state = S_ID; break; }     /* go to 'identifier' state */
          if ((c == '>')        /* if a '>' follows and previous */
          &&  (s.charAt(0) == '-')) {
            this.value = s.toString();
            return this.ttype = T_RGT;}/* char was a minus sign */
          this.ungetc(c);       /* put back last character, */
          this.value = s.toString().substring(0,s.length()-1);
          return this.ttype = T_ID;  /* return 'identifier' */

        case S_CMPOP:           /* --- comparison operator read */
          if ((c == '-')        /* if a minus sign follows and */
          &&  (s.charAt(0) == '<')) {  /* prev. char was a '<' */
            s.append('-');   this.ttype = T_LFT; }
          else if (c == '=') {  /* if an equal sign follows */
            s.append('=');   this.ttype = T_CMP; }
          else {                /* if anything else follows */
            this.ungetc(c);  this.ttype = s.charAt(0); }
          this.value = s.toString();
          return this.ttype;    /* and return the token read */

        case S_STRING:          /* --- quoted string */
          if ((c == '\n') || (c == EOF))  /* if end of line or file */
            throw new IOException("unterminated string" +this.lno());
          if (c != quote) {     /* if not at end of string */
            if (c == '\\') {    /* if escaped character follows, */
              state = S_ESC; break; }  /* go to escaped char state */
            s.append((char)c); break;  /* otherwise buffer character */
          }
          this.value = s.toString();
          return this.ttype = T_ID;    /* return 'identifier' */

        case S_ESC:             /* --- after '\' in quoted string */
          if ((c >= '0') && (c <= '7')) {        /* if octal digit, */
            ec = c -'0'; state = S_OCT1; break; }/* evaluate digit  */
          if (c == 'x') {       /* if hexadecimal character code, */
            state = S_HEX1; break;} /* go to hexadecimal evaluation */
          switch (c) {          /* evaluate character after '\' */
            case  'b': c = '\b'; break;
            case  'f': c = '\f'; break;
            case  'n': c = '\n'; break;
            case  'r': c = '\r'; break;
            case  't': c = '\t'; break;
            case '\n': c = -1;   break;
            default  :           break;
          }                     /* get escaped character and */
          if (c >= 0) s.append((char)c);   /* store it, then */
          state = S_STRING;     /* return to quoted string state */
          break;

        case S_OCT1:            /* --- escaped octal number 1 */
          if ((c >= '0')        /* if an octal digit follows, */
          &&  (c <= '7')) {     /* evaluate it */
            ec = ec *8 +c -'0'; state = S_OCT2; break; }
          this.ungetc(c);       /* otherwise put back last character */
          s.append((char)ec);   /* store escaped character and */
          state = S_STRING;     /* return to quoted string state */
          break;

        case S_OCT2:            /* --- escaped octal number 2 */
          if ((c >= '0') || (c <= '7'))
            ec = ec *8 +c -'0'; /* if octal digit, evaluate it */
          else this.ungetc(c);  /* otherwise put back last character */
          s.append((char)ec);   /* store escaped character and */
          state = S_STRING;     /* return to quoted string state */
          break;

        case S_HEX1:            /* --- escaped hexadecimal number 1 */
          if (ccl == C_DIGIT) { /* if hexadecimal digit, evaluate it */
            ec = c -'0';     state = S_HEX2; break; }
          if ((c >= 'a') && (c <= 'f')) {
            ec = c -'a' +10; state = S_HEX2; break; }
          if ((c >= 'A') && (c <= 'F')) {
            ec = c -'A' +10; state = S_HEX2; break; }
          this.ungetc(c);       /* otherwise put back last character */
          s.append('x');        /* store escaped character ('x') and */
          state = S_STRING;     /* return to quoted string state */
          break;

        case S_HEX2:            /* --- escaped hexadecimal number 2 */
          if (ccl == C_DIGIT)   /* if hexadecimal digit, evaluate it */
            ec = ec*16 +c -'0';
          else if ((c >= 'a') && (c <= 'f'))
            ec = ec*16 +c -'a' +10;
          else if ((c >= 'A') && (c <= 'F'))
            ec = ec*16 +c -'A' +10;
          else this.ungetc(c);  /* otherwise put back last character */
          s.append((char)ec);   /* store escaped character and */
          state = S_STRING;     /* return to quoted string state */
          break;

        case S_SLASH:           /* --- slash '/' */
          if (c == '/') {       /* if C++ style comment, then */
            state = S_CPPCOM; break; }   /* skip to end of line */
          if (c == '*') {       /* if C style comment */
            state = S_CCOM1; break; }    /* return to 1st state */
          this.ungetc(c);       /* otherwise put back last character */
          this.value = "/";     /* store character in buffer */
          return this.ttype = '/';     /* return `character' */

        case S_CPPCOM:          /* --- C++ style comment */
          if ((c == '\n')       /* if at end of line */
          ||  (c == EOF))       /* or at end of file */
            state = S_SPACE;    /* return to white space skipping */
          break;                /* (skip to end of line) */

        case S_CCOM1:           /* --- C style comment 1 */
          if      (c == EOF)    /* if end of file, abort */
            throw new IOException("unterminated comment" +this.lno());
          if      (c == '*')    /* if possibly 'end of comment', */
            state = S_CCOM2;    /* go to 2nd 'comment' state */
          else if (c == '/')    /* if possibly 'start of comment', */
            state = S_CCOM3;    /* go to 3rd 'comment' state */
          break;

        case S_CCOM2:           /* --- C style comment 2 */
          if      (c == EOF)    /* if end of file, abort */
            throw new IOException("unterminated comment" +this.lno());
          if      (c == '/') {  /* if end of comment found */
            if (--level <= 0) state = S_SPACE;
            else              state = S_CCOM1; }
          else if (c != '*')    /* if end of comment impossible */
            state = S_CCOM1;    /* return to comment skipping */
          break;                /* (possible start of comment) */

        case S_CCOM3:           /* --- C style comment 3 */
          if      (c == EOF)    /* if end of file, abort */
            throw new IOException("unterminated comment" +this.lno());
          if      (c == '*') {  /* if start of comment found */
            level++; state = S_CCOM1; }
          else if (c != '/')    /* if start of comment impossible */
            state = S_CCOM1;    /* return to comment skipping */
          break;                /* (possible end of comment) */

        default:                /* if state is illegal, abort */
          throw new IOException("illegal scanner state" +this.lno());

      }  /* switch() */
    }  /* while(1) */
  }  /* nextToken() */

  /*------------------------------------------------------------------*/

  public void ungetToken () { this.back = true; }
  public void pushBack   () { this.back = true; }

  /*------------------------------------------------------------------*/

  public void getChar (char c) throws IOException
  {                             /* --- check for a specific character */
    if (this.nextToken() != c)  /* check the next token */
      throw new IOException(((c != '\n') ? "'" +c +"'" : "'\\n'")
                            +" expected instead of '"
                            +this.value +"'" +this.lno());
  }  /* getChar() */

  /*------------------------------------------------------------------*/

  public void getID (String id) throws IOException
  {                             /* --- check for an identifier */
    if ((this.nextToken() != T_ID)  /* check the next token */
    &&  (this.ttype       != T_NUM))
      throw new IOException("identifier expected instead of '"
                            +this.value +"'" +this.lno());
    if (id == null) return;     /* if a specific id is given, */
    if (!id.equals(this.value)) /* compare the token value to it */
      throw new IOException("'" +id +"' expected instead of '"
                            +this.value +"'" +this.lno());
  }  /* getID() */

  public void getID () throws IOException
  { getID(null); }

  /*------------------------------------------------------------------*/

  public void getNumber () throws IOException
  {                             /* --- check for a number */
    if (this.nextToken() != T_NUM) /* check the next token */
      throw new IOException("number expected instead of \""
                            +this.value +"\"" +this.lno());
  }  /* getNumber() */

  /*------------------------------------------------------------------*/

  public static void main (String args[])
  {                             /* --- main function for testing */
    Scanner scanner;            /* scanner for testing */
    int     token;              /* next token */
    String  s;                  /* string to scan */

    try {                       /* test the scanner */
      switch (args.length) {    /* evaluate the argument list */
        case 0 : scanner = new Scanner("This is a test"); break;
        case 1 : scanner = new Scanner(args[0]);          break;
        default: scanner = new Scanner(new FileInputStream(args[0]));
                 break;
      }
      while (true) {            /* scan string until the end */
        token = scanner.nextToken();
        if ((token < 0) || (token == T_EOF)) break;
        System.out.println(token +" : " +scanner.value);
      } }                       /* print token and value */
    catch (IOException ioe) {
      System.err.println(ioe.getMessage()); }
  }  /* main() */

}  /* class Scanner */