Here is my code please draw a transition diagram and nfa on paper public class Lexer { private static final char EOF = 0; private static final int BUFFER_SIZE = 10; private Parser yyparser; // parent parser object private java.io.Reader reader; // input stream public int lineno; // line number public int column; // column // Double buffering implementation private char[] buffer1; private char[] buffer2; private boolean usingBuffer1; private int currentPos; private int bufferLength; private boolean endReached; // Keywords private static final String[] keywords = { "int", "print", "if", "else", "while", "void" }; public Lexer(java.io.Reader reader, Parser yyparser) throws Exception { this.reader = reader; this.yyparser = yyparser; this.lineno = 1; this.column = 0; // Initialize double buffering buffer1 = new char[BUFFER_SIZE]; buffer2 = new char[BUFFER_SIZE]; usingBuffer1 = true; currentPos = 0; bufferLength = 0; endReached = false; // Initial buffer fill fillBuffer(); } private void fillBuffer() throws Exception { char[] currentBuffer = usingBuffer1 ? buffer1 : buffer2; bufferLength = 0; while (bufferLength < BUFFER_SIZE) { int data = reader.read(); if (data == -1) { endReached = true; break; } currentBuffer[bufferLength++] = (char)data; } currentPos = 0; } public char NextChar() throws Exception { if (currentPos >= bufferLength) { if (endReached) { return EOF; } usingBuffer1 = !usingBuffer1; fillBuffer(); if (bufferLength == 0) { return EOF; } } char c = usingBuffer1 ? buffer1[currentPos] : buffer2[currentPos]; currentPos++; column++; if (c == '\n') { lineno++; column = 0; } return c; } public void UngetChar() { if (currentPos > 0) { currentPos--; column--; if (column < 0) { lineno--; // We don't know the previous line's length, so we'll set it to 0 column = 0; } } } public int Fail() { return -1; } private boolean isDigit(char c) { return c >= '0' && c <= '9'; } private boolean isLetter(char c) { return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z'); } private boolean isWhitespace(char c) { return c == ' ' || c == '\t' || c == '\n' || c == '\r'; } private String readIdentifier(char firstChar) throws Exception { StringBuilder sb = new StringBuilder(); sb.append(firstChar); while (true) { char c = NextChar(); if (isLetter(c) || isDigit(c) || c == '_') { sb.append(c); } else { UngetChar(); break; } } return sb.toString(); } private String readNumber(char firstDigit) throws Exception { StringBuilder sb = new StringBuilder(); sb.append(firstDigit); boolean hasDecimal = false; while (true) { char c = NextChar(); if (isDigit(c)) { sb.append(c); } else if (c == '.' && !hasDecimal) { hasDecimal = true; sb.append(c); } else { UngetChar(); break; } } return sb.toString(); } // * If yylex reach to the end of file, return 0 // * If there is a lexical error found, return -1 // * If a proper lexeme is determined, return token public int yylex() throws Exception { while (true) { char c = NextChar(); // Handle EOF if (c == EOF) { return 0; } // Skip whitespace if (isWhitespace(c)) { continue; } // Handle identifiers and keywords if (isLetter(c)) { String lexeme = readIdentifier(c); // Check if it's a keyword for (String keyword : keywords) { if (lexeme.equals(keyword)) { yyparser.yylval = new ParserVal((Object)lexeme); switch (keyword) { case "int": return Parser.INT; case "print": return Parser.PRINT; case "if": return Parser.IF; case "else": return Parser.ELSE; case "while": return Parser.WHILE; case "void": return Parser.VOID; } } } // Not a keyword, so it's an identifier yyparser.yylval = new ParserVal((Object)lexeme); return Parser.ID; } // Handle numbers if (isDigit(c)) { String number = readNumber(c); yyparser.yylval = new ParserVal((Object)number); return Parser.NUM; } // Handle operators and symbols switch (c) { case '(': yyparser.yylval = new ParserVal((Object)"("); return Parser.LPAREN; case ')': yyparser.yylval = new ParserVal((Object)")"); return Parser.RPAREN; case ';': yyparser.yylval = new ParserVal((Object)";"); return Parser.SEMI; case ',': yyparser.yylval = new ParserVal((Object)","); return Parser.COMMA; case '+': case '-': case '*': case '/': yyparser.yylval = new ParserVal((Object)String.valueOf(c)); return Parser.OP; case '<': case '>': case '=': char next = NextChar(); if (next == '=') { yyparser.yylval = new ParserVal((Object)(c + "=")); } else { UngetChar(); yyparser.yylval = new ParserVal((Object)String.valueOf(c)); } return Parser.RELOP; case '{': yyparser.yylval = new ParserVal((Object)"{"); return Parser.BEGIN; case '}': yyparser.yylval = new ParserVal((Object)"}"); return Parser.END; } // If we get here, we found an invalid character return Fail(); } } }