Coder.java

import java.sql.Time;
import java.util.concurrent.TimeUnit;

public class Coder {
    public static String start(String message) {

        StringBuilder result = new StringBuilder();

        for (char c : message.toCharArray()) {
            StringBuilder binaryCharWithEmptyParityBits = convertToBinaryWithParityBits(c);
            StringBuilder binaryCharWithCalculatedParityBits = Helpers.replaceParityBits(binaryCharWithEmptyParityBits);

            result.append(binaryCharWithCalculatedParityBits);
        }
        return result.toString();
    }

    /**
     * Converts single symbol to a binary String with 4 parity bits
     *
     * @param symbol char to convert
     * @return StringBuilder with 12 bits
     */
    public static StringBuilder convertToBinaryWithParityBits(char symbol) {
        StringBuilder binaryString = new StringBuilder();
        int val = symbol;
        for (int i = 0; i < 12; i++) {
            if (Helpers.checkPosition(i)) {
                binaryString.append(0);
            } else {
                binaryString.append((val & 128) == 0 ? 0 : 1);
                val <<= 1;
            }
        }
        return binaryString;
    }
}