[hardwired]

Code:

public class BraceCheck {
    public static void main(String[] args) {
        String[] tapes = {
            "01,{01,0,{10,1,{0,1},{1}}},1",
            "1,0,0{0}},{{{1,0}},1,0}",
            "0,1,{{0,0},{1},{{{0}},1"
        };
        for(int j = 0; j < tapes.length; j++) {
            System.out.printf("checkBraces(tapes[%d]): = %s%n",
                               j, checkBraces(tapes[j]));
        }
    }

    private static String checkBraces(String tape) {
        int len = tape.length();
        //System.out.println("len = " + len);
        int headPos = 0;
        // Find first left brace.
        while(tape.charAt(headPos) != '{' && headPos < len)
            headPos++;
        int leftBraceIndex = headPos;
        //System.out.printf("leftBraceIndex = %d%n", leftBraceIndex);
        // Find index of a matching right brace.
        int match = 0;
        do {
            headPos++;
            if(tape.charAt(headPos) == '{')
                match--;
            if(tape.charAt(headPos) == '}')
                match++;
        } while(headPos < len-1);

        String result = "ILLEGAL STATE";
        if(match < 1)
            result = "TOO MANY '{'";
        if(match == 1)
            result = "VALID DATA";
        if(match > 1)
            result = "TOO MANY '}'";
        return result;
    }
}