int转换为Java中的无符号char数组

Question

I'm trying to connect Android(Java) with Linux(Qt C++) using socket. After that I want to transfer length of message in bytes. For converting int in unsigned char array on the C++ side I use:

QByteArray IntToArray(qint32 source) 
{
    QByteArray tmp;
    QDataStream data(&temp, QIODevice::ReadWrite);
    data << source;
    return tmp;
}

But I don't know how I can do the same converting on the Java side , because Java hasn't unsigned types. I tried to use some examples but always got different results. So, I need Java method which returns this for source = 17:

0x00 , 0x00 , 0x00 , 0x11

I understand that it's a very simple question, but I'm new in Java so it's not clear to me.

UPD:

Java:

PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
out.print(ByteBuffer.allocate(4).putInt(17).array());

Qt C++:

 QByteArray* buffer = new QByteArray();
 buffer->append(socket->readAll());

Output:

buffer = 0x5b , 0x42 , 0x40 , 0x61 , 0x39 , 0x65 , 0x31 , 0x62 , 0x66 , 0x35 .

UPD2:

Java:

out.print(toBytes(17));
...
 byte[] toBytes(int i)
        {
            byte[] result = new byte[4];

            result[0] = (byte) (i >> 24);
            result[1] = (byte) (i >> 16);
            result[2] = (byte) (i >> 8);
            result[3] = (byte) (i /*>> 0*/);

            return result;
        }

Qt C++: same

Output:

buffer = 0x5b , 0x42 , 0x40 , 0x63 , 0x38 , 0x61 , 0x39 , 0x33 , 0x38 , 0x33 .

UPD3:

Qt C++:

 QByteArray buffer = socket->readAll();
    for(int i = 0; i < buffer.length(); ++i){
        std::cout << buffer[i];
    }
    std::cout<<std::endl;

Output:

[B@938a15c

Answer 1

First of all, don't use PrintWriter .

Here's something to remember about Java I/O:

• Streams are for bytes , Readers/Writers are for characters .
• In Java, a character is not a byte. Characters have an encoding associated with them, like UTF-8. Bytes don't.

When you wrap a Stream in a Reader or a Writer , you are taking a byte stream and imposing a character encoding on that byte stream. You don't want that here.

Just try this:

    OutputStream out = socket.getOutputStream();
    out.write(toBytes(17));