public String getStringValue(int offset) {
        if (mValue == null || offset > mValue.length) return null;
        byte[] strBytes = new byte[mValue.length - offset];
        for (int i = 0; i != (mValue.length - offset); ++i) strBytes[i] = mValue[offset + i];
        return new String(strBytes);
    }
Used for mocks and constants in rxandroidble, but instances created in mockrxandroidble, so the methods must be implemented
rxandroidble/src/test/java/android/bluetooth/BluetoothGattCharacteristic.java