Objectives of the project 1 To develop your understanding of

Objectives of the project 1. To develop your understanding of lexical analyzer in compilers of program languages. 2. To improve you knowledge of Java programming. Topic of assignment: Lexical analyzer Write Java programs for a lexical analyzer which can identify the following tokens: 1 INT_LIT: consists of digits 2 ID_CODE: starts with a letter followed by letters and digits, and has a limited length of 10 3 ASSIGN_CODE: = 4 PLUS_CODE: + 5 MINUS_CODE: - 6 DIVISON_CODE: / 7 MULTIP_CODE: * Programs You will design two classes: TestLexAnalyzer: contains main method which performs input/output operations. LexAnalyzer: contains all the methods related to lexical analysis. Refer to the C programs in the text book for algorithm design. Input: a string of assignment statement Output: tokens of each lexeme. A running example: Input string: sum = sum + num; Output: Lexeme Token sum ID_CODE = ASSIGN_CODE sum ID_CODE + PLUS_CODE num ID_CODE using java source code

Solution

LexAnalyzer class

public class LexAnalyzer {
String str;
public LexAnalyzer(String str1) {
   str=new String();
   str=str1;
}
void tokenize()
{ boolean check=true;
   for(int i=0;i<str.length();i++)
   {
   if(str.charAt(i)==\'+\'&&check)
   {
       System.out.print(\" + PLUS_CODE \");
   }
   if(str.charAt(i)==\'-\'&&check)
   {
       System.out.print(\" - PLUS_CODE \");
   }
   if(str.charAt(i)==\'*\'&&check)
   {
       System.out.print(\" * PLUS_CODE \");
   }
   if(str.charAt(i)==\'/\'&&check)
   {
       System.out.print(\" / PLUS_CODE \");
   }
   if(str.charAt(i)==\'=\'&&check)
   {
       System.out.print(\" = ASSIGN_CODE \");
   }
   if(str.charAt(i)==\'0\'||str.charAt(i)==\'1\'||str.charAt(i)==\'2\'||str.charAt(i)==\'3\'||str.charAt(i)==\'4\'||str.charAt(i)==\'5\'||str.charAt(i)==\'6\'||str.charAt(i)==\'7\'||str.charAt(i)==\'8\'||str.charAt(i)==\'9\')
   {
       if(check==true)
       {
           check=false;
       }
       else
       {
           if(str.charAt(i)==\'0\'||str.charAt(i)==\'1\'||str.charAt(i)==\'2\'||str.charAt(i)==\'3\'||str.charAt(i)==\'4\'||str.charAt(i)==\'5\'||str.charAt(i)==\'6\'||str.charAt(i)==\'7\'||str.charAt(i)==\'8\'||str.charAt(i)==\'9\')
           {
               System.out.print(str.charAt(i-1)+\"\"+str.charAt(i)+\" INT_LIT\");
               check=true;
           }
           else
           {
               System.out.println(\"String contain invalid token: digit followed by character\");
               break;
           }
       }
   }
   if(Character.isAlphabetic(str.charAt(i)))
   {
       int j=i;
       boolean flag=true;
       while(i<str.length()&&(Character.isAlphabetic(str.charAt(i))||Character.isDigit(str.charAt(i))))
       {
           i++;
           if(i-j>10)
           {
               System.out.println(\"String contain invalid token: It contain to\");
               flag=false;
               break;
           }
       }
       if(!flag)
       {
           break;
       }
       else
       {
       System.out.print(str.substring(j,i)+\" ID_CODE\");
       i--;
       }
   }
   }
}
}

TestLexAnalyzer class

import java.util.Scanner;

public class TestLexAnalyzer {

   public static void main(String[] args) {
       Scanner sc=new Scanner(System.in);
       System.out.println(\"Enter the string to tokenize\");
       String str=sc.nextLine();
       LexAnalyzer lexAnalyzer=new LexAnalyzer(str);
       lexAnalyzer.tokenize();
       sc.close();
       }

}

Output:

Enter the string to tokenize
sum=sum+num
sum ID_CODE = ASSIGN_CODE sum ID_CODE + PLUS_CODE num ID_CODE