Lexical Analyzer Implementation

Use Java to write a simple Lexical Analyzer.

Input: a source code file, (.txt file). Ask user to input the file name.

Output: printing all recognized tokens

The source code accepted tokens include

Keywords: int double String (case sensitive)

operators: = ( ) + - * / , ;

identifier: letter(letter|digit)*

int constant

double constant

string constant: string constant is enclosed in a pair of "", such as "abc"

anything not recognized is detected as errors

If the input file has the following content:

int a, b=10;

a =bc*10-&(3.2+"abc";

The output should be

Line1:1 keyword: int

Line1: 5 identifier: a

Line1:6 operator: ,

Line1: 7 identifier: b

Line1: 8 operator: =

Line1: 9 int constant: 10

Line1: 11 operator: ;

Line2: 1 identifier: a

Line2: 3 operator: =

Line2: 4 identifier: bc

Line2: 6 operator: *

Line2: 7 int constant: 10

Line2: 9 operator: -

Line2: 10 error: & not recognized

Line2: 11 operator: (

Line2: 12 double constant: 3.2

Line2: 15 operator: +

Line2: 16 string constant: "abc"

Line2: 21 operator: ;