Notes

import java.util.Scanner;



class G {
static int sCurrentToken = 0;

static int LEFT_PAREN = 11; // '('
static int RIGHT_PAREN = 12; // ')'
static int INT = 13; // e.g., '123', '+123', '-123'
static int STRING = 14; // "string's (example)." (strings do not extend
// across lines)
static int DOT = 15; // '.'
static int FLOAT = 16; // '123.567', '123.', '.567', '+123.4', '-.123'
static int NIL = 17; // 'nil' or '#f', but not 'NIL' nor 'nIL'
static int T = 18; // 't' or '#t', but not 'T' nor '#T'
static int QUOTE = 19; // '
static int SYMBOL = 20; // a consecutive sequence of printable characters
// that are
// not numbers, and do not contain '(', ')', single-quote,
// double-quote and white-spaces ;
// Symbols are case-sensitive
// (i.e., uppercase and lowercase are different);

static char sCurrentCh = '' ;

} // class G

class Main {

public static void main(String[] args) throws Throwable {
System.out.println("TEST!");
Tokenizer lex = new Tokenizer() ;
lex.run();

}

} // class Main

class Tokenizer {
StringBuffer mTokenString = new StringBuffer() ;
int mToken = 0;

int Get() throws Throwable {
int tok = mToken;
this.run();
return tok;
} // Get()

void GetCh() throws Throwable {

G.sCurrentCh = (char) System.in.read();
} // GetCh()

void run() throws Throwable {
int token = 0;
// Scanner s = new Scanner(System.in);
while (G.sCurrentCh != -1 ) {
ReadSpilt();
token = Recognize();
System.out.println("token:>" + token + " <" );
} // while not eof

System.out.println("over");
} // run()

void ReadSpilt() throws Throwable { // set "mTokenString" to each pattern
// like: ()' whitespace and strs
char inputCh = '';
GetCh() ;
inputCh = G.sCurrentCh ;
if (inputCh == '(' || inputCh == '}' || inputCh == ''') {
mTokenString.append(inputCh);
} // if ()' set mTokenString
else {
while (inputCh != '(' && inputCh != '}' && inputCh != '''
&& inputCh != ' ' && inputCh != -1 && inputCh != 'n' ) {
mTokenString.append(inputCh);
GetCh() ;
inputCh = G.sCurrentCh ;
} // while not delimiter
} // else
} // ReadSpilt()

int Recognize() throws Throwable {
int tokenType = 0;
if (mTokenString.equals("(")) {
tokenType = G.LEFT_PAREN;
} // if
else if (mTokenString.equals(")")) {
tokenType = G.RIGHT_PAREN;
} // else if
else if (isStrInt(mTokenString.toString())) {
tokenType = G.INT;
} // else if
else if (isStrString(mTokenString.toString())) {
tokenType = G.STRING;
} // else if
else if (isDot(mTokenString.toString())) {
tokenType = G.DOT;
} // else if
else if (isStrFloat(mTokenString.toString())) {
tokenType = G.FLOAT;
} // else if
else if (isStrNil(mTokenString.toString())) {
tokenType = G.NIL;
} // else if
else if (isStrT(mTokenString.toString())) {
tokenType = G.T;
} // else if
else if (isStrQuote(mTokenString.toString())) {
tokenType = G.QUOTE;
} // else if
else {
tokenType = G.SYMBOL;
} // else

return tokenType;
} // Recognize()

private boolean isStrQuote(String string) throws Throwable {
if (string.equals("'"))
return true;
return false;
} // isStrQuote(String string)

private boolean isStrT(String string) throws Throwable {
if (string.equals("t") || string.equals("#t"))
return true;
return false;
} // isStrT(String string)

private boolean isStrNil(String string) throws Throwable {
if (string.equals("nil") || string.equals("#f"))
return true;
return false;
} // isStrNil(String string)

private boolean isStrFloat(String string) throws Throwable {
if (Character.isDigit(string.charAt(0))) {
return isStrUnsignFloat(string);
} // if first char is digit
else if (string.charAt(0) == '+' || string.charAt(0) == '-') {
return isStrUnsignFloat(string.substring(1));
} // else if

else
return false;
} // isStrFloat(String string)

private boolean isStrUnsignFloat(String string) throws Throwable {
boolean hasDot = false;
if (Character.isDigit(string.charAt(0))) {
for (int i = 0; i < string.length(); i++) {
if (string.charAt(i) == '.' && hasDot)
return false; // already has '.' but see again
else if (string.charAt(i) == '.')
hasDot = true; // first see '.'
// if encounter '.'
else {
if (!Character.isDigit(string.charAt(i)))
return false;
} // else not '.'
} // for
} // if first is digit

return true;

} // isStrUnsignFloat( String string )

private boolean isDot(String string) throws Throwable {
// TODO Auto-generated method stub
return false;
} // isDot(String string)

private boolean isStrString(String string) throws Throwable {

return false;
} // isStrString(String string)

private boolean isStrInt(String string) throws Throwable {
return false ;
} // isStrInt( String string )

/*
* char ch = GetCh() ; mCurrentTok.append(ch) ;
*/

} // class Tokenizer