TwelveBitSignExtender.java

 private static void PUSHI(String dataHex) {
        String builder = "";
        for (int i = 0; i < dataHex.length(); i++) {
            switch (dataHex.substring(i, i + 1)) {
                case "0":
                    builder += "0000";
                    break;
                case "1":
                    builder += "0001";
                    break;
                case "2":
                    builder += "0010";
                    break;
                case "3":
                    builder += "0011";
                    break;
                case "4":
                    builder += "0100";
                    break;
                case "5":
                    builder += "0101";
                    break;
                case "6":
                    builder += "0110";
                    break;
                case "7":
                    builder += "0111";
                    break;
                case "8":
                    builder += "1000";
                    break;
                case "9":
                    builder += "1001";
                    break;
                case "A":
                    builder += "1010";
                    break;
                case "B":
                    builder += "1011";
                    break;
                case "C":
                    builder += "1100";
                    break;
                case "D":
                    builder += "1101";
                    break;
                case "E":
                    builder += "1110";
                    break;
                case "F":
                    builder += "1111";
                    break;
                default:
                    break;
            }
        }
        String sign = builder.substring(0, 1);
        String sExt = "";

        if (sign.equals("1")) {
            for (int i = builder.length(); i < 16; i++) {
                sExt += "1";
            }
        } else if (sign.equals("0")) {
            for (int i = builder.length(); i < 16; i++) {
                sExt += "0";
            }
        }
        builder = sExt + builder;

        //System.out.println(builder);

        String b2HEX = "";
        for (int i = 0 ; i < builder.length(); i+=4){
            switch (builder.substring(i, i + 4)) {
                case "0000":
                    b2HEX += "0" ;
                    break;
                case "0001":
                    b2HEX += "1";
                    break;
                case "0010":
                    b2HEX += "2";
                    break;
                case "0011":
                    b2HEX += "3";
                    break;
                case "0100":
                    b2HEX += "4";
                    break;
                case "0101":
                    b2HEX += "5";
                    break;
                case "0110":
                    b2HEX += "6";
                    break;
                case "0111":
                    b2HEX += "7";
                    break;
                case "1000":
                    b2HEX += "8";
                    break;
                case "1001":
                    b2HEX += "9";
                    break;
                case "1010":
                    b2HEX += "A";
                    break;
                case "1011":
                    b2HEX += "B";
                    break;
                case "1100":
                    b2HEX += "C";
                    break;
                case "1101":
                    b2HEX += "D";
                    break;
                case "1110":
                    b2HEX += "E";
                    break;
                case "1111":
                    b2HEX += "F";
                    break;
                default:
                    break;
            }
        }
       // System.out.println(b2HEX);

        short st = (short) Integer.parseInt(b2HEX, 16);

        System.out.println(st);
        
    }