用JAVA写词法分析器.doc

import java.lang.*; import java.io.*; public class Wordanalsys { static char ch; static int index=0; static int j=0; static char allstr[]=new char[100000]; static String name; public char Getchar(){ try{ ch=(char)System.in.read(); }catch(Exception e){e.printStackTrace();} return ch; } public boolean IsLetter(char ch){ return java.lang.Character.isLetter(ch); } public boolean IsDigit(char ch){ return java.lang.Character.isDigit(ch); } public int Reserve(){ KeyTable table[]=new KeyTable[5]; table[0]=new KeyTable(while,1); table[1]=new KeyTable(for,2); table[2]=new KeyTable(if,3); table[3]=new KeyTable(else,4); table[4]=new KeyTable(int,5); name=new String(allstr).substring(j,index);//取子串 for(int i=0;i5;i++) if(name.equals(table[i].key)) return table[i].code; return 0; } public static void main (String[] args) { Wordanalsys a=new Wordanalsys(); ch=a.Getchar(); int m=0; while(ch!=#){ allstr[index]=ch; index++; ch=a.Getchar(); } int k=index; index=0; while(jk-1) { m=j; if(a.IsLetter(allstr[j])){ while(a.IsLetter(allstr[index])||a.IsDigit(allstr[index])){ index++; } if(a.Reserve()!=0) System.out.println(保留字 +name+ +a.Reserve()); else System.out.println(标识符 + 6); j=index; } if(a.IsDigit(allstr[j])){ while(a.IsDigit(allstr[index]))index++; name=new String(allstr).substring(j,index); int b=java.lang.Integer.pa sint(name); String name1=Integer.toBinaryString(b) ; System.out.println(数字 +name+ 7+name1); j=index; } if(allstr[j]==(){System.out.prin