CSV Parser (using State Machine) in Java

Eric — Wed, 29 Aug 2012 15:26:52 +0000
import java.util.ArrayList;

public class CSVParser {

	public enum OPstates
	{
		INITIAL(0),
		NORMAL(1),
		COMMA(2),
		OPEN_QUOTATION(9),
		CLOSE_QUOTATION(4),
		WHITE_SPACE(5),
		QUOTATION_IN_TOKEN(6),
		CLOSE_QUOTATION_IN_TOKEN(8),
		ERROR(-1),
		NEW_LINE(200);

		int i;
		private OPstates(int i) {
			this.i = i;
		}

		public int getValue()
		{
			return i;
		}
	}
	int [][] state = {	{1, 2, 3, 200, 5},      //0 initial state
						{1, 2, -1, 200, 1},     //1 normal character state
						{1, 2, 3, 200, 5},      //2 comma state
						{9, 9, 4, -1, 9},       //3 open quotation
						{-1, 2, 6, 200, 5},     //4 close quotation or quotation in token state
						{1, 2, 3, 200, 5},      //5 whitespace state
						{6, 6, 7, 200, 6},      //6 quotation in token
						{-1, -1, 8, -1, -1},    //7 close quotation
						{9, -1, 4, 200, 9},     //8 close quotation
						{9, 9, 4, -1, 9}        //9 open quotation state
					 };

	ArrayList tokens = new ArrayList();
	int TokenState(char token)
	{
		if(token == ',')
			return 1;
		else if(token == '"')
			return 2;
		else if(token == '\n')
			return 3;
		else if(token == ' ')
			return 4;
		else
			return 0;
	}

	void Parse(String input)
	{
		int curState = 0;
		StringBuilder sb = new StringBuilder();
		for(int i = 0; i < input.length(); i++)
		{
			char tokenChar = input.charAt(i);
			int tokenState = TokenState(tokenChar);
			curState = state[curState][tokenState];
			if(curState == OPstates.NORMAL.getValue() ||
					curState == OPstates.OPEN_QUOTATION.getValue() ||
					curState == OPstates.QUOTATION_IN_TOKEN.getValue() ||
					curState == OPstates.CLOSE_QUOTATION_IN_TOKEN.getValue())
				sb.append(tokenChar);

			if(curState == OPstates.COMMA.getValue() ||
					curState == OPstates.NEW_LINE.getValue())
			{
				tokens.add(sb.toString().trim());
				sb.delete(0, sb.length());

				if(curState == OPstates.NEW_LINE.getValue())
					break;
			}

			if(curState == OPstates.ERROR.getValue())
				throw new RuntimeException("Parse Error");
		}
	}

	@Override
	public String toString() {
		StringBuilder sb = new StringBuilder();

		for(int i = 0; i < tokens.size(); i++)
			sb.append("Token: " + tokens.get(i) + "\n");

		return sb.toString().trim() + "\n";
	}

	public CSVParser(String input) {
		Parse(input);
	}

	public static void main(String[] args) {
		String s = "   \"a\" ,    \"b,cd\"      ,   c ,\"vb,  n\",\",\"\n";
		System.out.println(s + new CSVParser(s));

		s = "    ,   a,b,\"c, l\",d,,5\n";
		System.out.println(s + new CSVParser(s));

		s = "h,\"john, jr\",a,b,\"c, l\",d,,5,\"e, jr\"\n";
		System.out.println(s + new CSVParser(s));

		s = "\"h, jk\",\"john, jr\",a,b,\"c, l\",d,,5,\"e's, jr\"\n";
		System.out.println(s + new CSVParser(s));

		s = "\"  e   \"\"abc\"\" n \"\"def\"\" \"\"buddy\"\"d\",\"b, jr\",  c dj n\n";
		System.out.println(s + new CSVParser(s));
	}
}
Parser – Random Code Generator

CSV Parser (using State Machine) in Java
