Java - 想要将整数值类型转换为字节，以便我可以以二进制格式写入文件

Question

I'm trying to convert an Integer (32 bits or 4 Bytes) to a Byte array and write to a file ONLY the first Byte of that integer truncated.

DataOutputStream os = new DataOutputStream(new FileOutputStream(fileChooser.getSelectedFile() + ".soit"));

byte[] bytes = ByteBuffer.allocate(4).putInt(511).array();
for (byte b : bytes) {
    System.out.format("0x%x ", b);
    try {
        os.write(bytes, 0, 1);
    } catch (IOException ex) {
        Logger.getLogger(p8r_planning.class.getName()).log(Level.SEVERE, null, ex);
    }
}

Here's a snippet of my code, which sadly creates the file but does not contain any data, however my System.out.format line, does print out the expected results.

0x0 0x0 0x1 0xff

in this case, I only want the very first byte (0xff) written to my file in binary format. Like this:

11111111

Can someone point to me what I might have done wrong?

Answer 1

I would use the writeInt on DataOutputStream which write it as big endian

try (DataOutputStream os = new DataOutputStream(
                           new FileOutputStream(
                               fileChooser.getSelectedFile() + ".soit"))) {
   os.writeByte((byte) 511); // write just the lowest 8-bits.
}