How to divide into 3 java files. Lexer.java, Main.java, and Token.java

import java.io.File; import java.io.FileNotFoundException; import java.util.ArrayList; import java.util.Scanner; import java.util.regex.Matcher; import java.util.regex.Pattern;

public class Lexer { public static enum TokenType { // Token types cannot have underscores NUMBER("-?[0-9]+"), BINARYOP("[*|/|+|-]"), WHITESPACE("[ \t\f ]+");

public final String pattern;

private TokenType(String pattern) { this.pattern = pattern; } }

public static class Token { public TokenType type; public String data;

public Token(TokenType type, String data) { this.type = type; this.data = data; }

@Override public String toString() { return String.format("(%s %s)", type.name(), data); } }

public static ArrayList lex(String input) { // The tokens to return ArrayList tokens = new ArrayList();

// Lexer logic begins here StringBuffer tokenPatternsBuffer = new StringBuffer(); for (TokenType tokenType : TokenType.values()) tokenPatternsBuffer.append(String.format("|(?<%s>%s)", tokenType.name(), tokenType.pattern)); Pattern tokenPatterns = Pattern.compile(new String(tokenPatternsBuffer.substring(1)));

// Begin matching tokens Matcher matcher = tokenPatterns.matcher(input); while (matcher.find()) { if (matcher.group(TokenType.NUMBER.name()) != null) { tokens.add(new Token(TokenType.NUMBER, matcher.group(TokenType.NUMBER.name()))); continue; } else if (matcher.group(TokenType.BINARYOP.name()) != null) { tokens.add(new Token(TokenType.BINARYOP, matcher.group(TokenType.BINARYOP.name()))); continue; } else if (matcher.group(TokenType.WHITESPACE.name()) != null) continue; }

return tokens; }

public static void main(String[] args) { //creating file object File file = new File("input.txt"); //scanner object to scan the input file Scanner sc = null; String input = ""; try { sc = new Scanner(file); //traversing the entire input file untile all the lines found while (sc.hasNextLine()) { input += sc.nextLine()+" "; } } catch (FileNotFoundException e) { System.out.println("File Not Found. Please Check Input File"); } // Create tokens and print them ArrayList tokens = lex(input); for (Token token : tokens) System.out.println(token); } }