Java simple implementation of compiler principle lexical analysis

Package Com.csray;import Java.io.bufferedreader;import Java.io.file;import java.io.filenotfoundexception;import Java.io.filereader;import Java.io.ioexception;public class Lexicalanalysis {static String id;public static void Main ( String[] args) throws ioexception{lexicalanalysis la = new Lexicalanalysis (); String context =//la. bufferedreaderdemo//("C:" +system.getproperty ("file.separator") + "Users" +system.getproperty ("file.separator") + " Administrator "+system.getproperty (" file.separator ") +" Desktop "+system.getproperty (" file.separator ") +" Lexical "); La. Bufferedreaderdemo ("c:\\users\\administrator\\desktop\\lexical\\lexical.c"); SYSTEM.OUT.PRINTLN (context); for (int i = 0; i < context.length ();) {char NOWC = Context.charat (i);//system.out.println (NOWC); if (NOWC = = "| | nowc = = ' \ n ' | | nowc = = ' \ t ') {id =" illegalcharacter "; ++i;} else if (Isalpha (NOWC)) {i = alphaprocess (context, NOWC, i);} else if (IsDigit (NOWC)) {i = digitprocess (context, NOWC, i);//i ++;} else {i = otherprocess (context, NOWC, i);//i++;}}} Read the lexical.c file to Stringpublic string Bufferedreaderdemo (String path) throws Ioexception{file file = new file (p ATH); if (!file.exists () | | | file.isdirectory ()) throw new FileNotFoundException (); BufferedReader br = new BufferedReader (new FileReader (file)); String tmp = NULL; StringBuffer Sbuff = new StringBuffer (); tmp = Br.readline (); while (tmp! = null) {Sbuff.append (tmp+ ""); tmp = Br.readline (); }return sbuff.tostring ();} alphaprocesspublic static int alphaprocess (String context, char c, int i) {StringBuffer word = new StringBuffer (); while ( Isalpha (c)) | | (IsDigit (c)) | | c = = ' _ ') {Word.append (c); c = Context.charat (++i);} System.out.println (Word.tostring ());//check this word if or not a keywordif (Checkkeyword (word.tostring ())) {id = " Iskeyword "; System.out.println ("(" + word.tostring () + "," + ID + ")"); else {id = "Iscommonword"; System.out.println ("(" + word.tostring () + "," + ID + ")"); return i;} Checkkeywordpublic Static Boolean Checkkeyword (string word) {string keyword = ' Auto double int struct break else long ' switch case enum register typedef char ' + ' extern return Union const float Short Unsigned continue for signed void default goto "+" sizeof volatile does if while static Scnaf printf "; string[] KeyWords = Keyword.split (""); for (int i = 0; i < keywords.length; ++i) {if (Word.equals (Keywords[i])) {return true;}} return false;} digitprocesspublic static int digitprocess (String context, char c, int i) {stringbuffer digit = new StringBuffer (); while (IsDigit (c)) {digit.append (c); c = Context.charat (++i);} id = "IsDigit"; System.out.println ("(" + digit.tostring () + "," + ID + ")"); return i;} otherprocesspublic static int otherprocess (String context, char c, int i) {//+/() {} + =/= & "" StringBuffer O Perator = new StringBuffer (); StringBuffer delimiter = new StringBuffer (), if (c = = ' + ') {operator.append (c); id = "Isoperator"; c = Context.charat (++i); if (c = = ' = ') {operator.append (c); System.out.println ("(" + operator + "," + ID + ")"); return ++i;} else if (c = = ' + ') {operator.append (c); System.out.println ("(" + operator + "," + ID + ")"); return ++i;} else {System.out.println ("+ operator +", "+ ID +") "); return---------;} else if (c = = ' (') {delimiter.append (c); id = "Isdelimiter"; System.out.println ("(" + delimiter + "," + ID + ")"); return ++i;} else if (c = = ') ') {delimiter.append (c); id = "Isdelimiter"; System.out.println ("(" + delimiter + "," + ID + ")"); return ++i;} else if (c = = ' {') {delimiter.append (c); id = "Isdelimiter"; System.out.println ("(" + delimiter + "," + ID + ")"); return ++i;} else if (c = = '} ') {delimiter.append (c); id = "Isdelimiter"; System.out.println ("(" + delimiter + "," + ID + ")"); return ++i;} else if (c = = '; ') {delimiter.append (c); id = "Isdelimiter"; System.out.println ("(" + delimiter + "," + ID + ")"); return ++i;} else if (c = = ' = ') {operator.append (c); id = "Isoperator"; c = Context.charat (++i); if (c = = ' = ') {operator.append (c); System.out.println ("(" + operator + "," + ID + ")"); return ++i;} else {System.out.println ("(" + OPerator + "," + ID + ")"); return i;}} else if (c = = '/') {operator.append (c); c = Context.charat (++i); if (c = = ' = ') {operator.append (c); id = "Isoperator"; System.out.println ("(" + operator + "," + ID + ")"); return ++i;} else if (c = = '/') {operator.append (c); id = "Isannotation"; c = Context.charat (++i); while (c! = ") {operator.append (c); C = Co Ntext.charat (++i);} System.out.println ("(" + operator + "," + ID + ")"); return i;}} else if (c = = ' & ') {operator.append (c); id = "Isoperator"; System.out.println ("(" + operator + "," + ID + ")"); return ++i;} else if (c = = ' "') {delimiter.append (c); id =" Isdelimiter "; System.out.println ("(" + delimiter + "," + ID + ")"); return ++i;} else if (c = = ', ') {delimiter.append (c); id = "Isdelimiter"; System.out.println ("(" + delimiter + "," + ID + ")"); return ++i;} else if (c = = '% ') {operator.append (c); id = "Isoperator"; c = Context.charat (++i); if (c = = ' d ') {operator.append (c); System.out.println ("(" + operator + "," + ID + ")"); return ++i;} Return-----; return i;} IsdIgitpublic Static Boolean isdigit (char c) {if (c >= ' 0 ' && C <= ' 9 ') return True;return false;} Isalphapublic Static Boolean isalpha (char c) {if (C >= ' a ' && C <= ' Z ') return True;else if (c >= ' a ' & & c <= ' z ') return True;return false;}}

Instance:

Testint Main () {float Nu0_m;int num = 100;num++; scanf ("%d", &num);p rintf ("%d", num); return 0;}

Results:

Test int main () {  float nu0_m; int num = num++  ; scanf ("%d", &num); printf ("%d", num); return 0; } (//test, isannotation) (int, Iskeyword) (Main, Iscommonword) ((, Isdelimiter) (), Isdelimiter) ({, isdelimiter) (Flo At, Iskeyword) (Nu0_m, Iscommonword) (;, isdelimiter) (int, iskeyword) (num, iscommonword) (=, isoperator) (ISDI) git) (;, isdelimiter) (num, Iscommonword) (+ +, isoperator) (;, Isdelimiter) (scanf, Iscommonword) ((, Isdelimiter) (", Isdelimiter) (%d, Isoperator) (", Isdelimiter) (,, Isdelimiter) (&, isoperator) (num, Iscommonword) (), Isdelimiter) (;, Isdelimiter) (printf, Iskeyword) ((, Isdelimiter) (", Isdelimiter) (%d, Isoperator) (", Isdelimiter) (,, isdelimiter) (num, Iscommonword) (), Isdelimiter ) (;, Isdelimiter) (Return, Iskeyword) (0, IsDigit) (;, Isdelimiter) (}, Isdelimiter)

　　

Java simple implementation of compiler principle lexical analysis