Lexical Analyser

## Input File (input.txt)

int main() {
 int a=20,65b=10;   
 cout << "Hello" << endl;
    return 0;
}



## Lexical Analyser Code

import java.io.*;

public class Lexic_analyzer {

	String keywords[]={"int","float","cout","cin","for","endl","return"};
	char symbols[]={'.','+','-','*','/','=','(',')',',','{','}',':',';','>','<'};
	String cur,temp="";
	
	boolean iskeyword(String str){
		for(int i=0;i<keywords.length;i++){
			if(str.equals(keywords[i])){
				return true;
			}
		}
		return false;
	}
	
	boolean isSymbol(char ch){
		for(int i=0;i<symbols.length;i++){
			if(ch == symbols[i]){
				return true;
			}
		}
		return false;
	}
	
	void seprator(String str){
		int i=0;
		String temp="";
		while(i< str.length()){
			char ch=str.charAt(i);
			if((Character.isAlphabetic(ch)) || (Character.isDigit(ch))){
				temp=temp+ch;
				if(iskeyword(temp)){
					System.out.println(temp+" is a keyword");
					temp="";
				}
				if((i == str.length()-1) && (temp.length() !=0)){
					if(Character.isDigit(temp.charAt(0))){
						System.out.println(temp+" is a constant");
                                                temp="";
					}
					else{
						System.out.println(temp+" is a identifier");
                                                temp="";
					}
				}
			}
			else if(isSymbol(ch)){
				if(temp.length() !=0){
					if(iskeyword(temp)){
						System.out.println(temp+" is a keyword");
						temp="";
					}
					else if(Character.isDigit(temp.charAt(0))){
						System.out.println(temp+" is a constant");
						temp="";
					}
					else{
						System.out.println(temp+" is a identifier");
						temp="";
					}
				}
				System.out.println(ch+" is a symbol");
			}
			i++;
		}
	}
	
	public static void main(String[] args) {
		try{
			FileReader in=new FileReader("input.txt");
			BufferedReader br=new BufferedReader(in);
			Lexic_analyzer la=new Lexic_analyzer();
		
			la.cur=br.readLine();
			while(la.cur != null){
				int i=0;
				int len=la.cur.length();
				while(i < len){
					char ch=la.cur.charAt(i);
					if(ch != ' '){
						la.temp=la.temp+ch;
					}
					else{
						la.seprator(la.temp);
						la.temp="";
					}
					i++;
				}
				la.seprator(la.temp);
				la.temp="";
				la.cur=br.readLine();
			}
			br.close();
	}catch(Exception e){
		System.out.println(e);
	}
	}
}


## Output
int is a keyword
main is a identifier
( is a symbol
) is a symbol
{ is a symbol
int is a keyword
a is a identifier
= is a symbol
20 is a constant
, is a symbol
65b is a constant
= is a symbol
10 is a constant
; is a symbol
cout is a keyword
< is a symbol
< is a symbol
< is a symbol
< is a symbol
endl is a keyword
; is a symbol
return is a keyword
0 is a constant
; is a symbol
} is a symbol