Thread: Java equivalent of Python’s struct.pack?

Is there any function equivalent to Python's struct.pack in Java that allows me to pack and unpack values like this?

pump_on = struct.pack("IIHHI", 0, 0, 21, 96, 512)
event = open(("/dev/input/event7"), "r+",0)
event.write(valve_on)

I take it you're actually creating a struct of a files contents there, in theory you could do this with a byte array.

This might not be what you want and there might be a more simple solution to this but at least it works

    public static void main(String[] args) throws Throwable {
        // Create a "struct" or a buffer that we wish to output
        final ByteBuffer outputByteBuffer = ByteBuffer.allocate(30);
        outputByteBuffer.putChar('I').putChar('I').putChar('H').putChar('H').putChar('I').putInt(0).putInt(0).putInt(21).putInt(96).putInt(512);
        outputByteBuffer.flip();
 
        // Write the buffer to a file
        final File file = new File("/dev/input/event7");
        final FileOutputStream fileOutputStream = new FileOutputStream(file);
        fileOutputStream.getChannel().write(outputByteBuffer);
        fileOutputStream.close();
 
        // Open the file and read in the buffer
        final ByteBuffer inputByteBuffer = ByteBuffer.allocate(30);
        final FileInputStream fileInputStream = new FileInputStream(file);
        fileInputStream.getChannel().read(inputByteBuffer);
        fileInputStream.close();
 
        // Each character takes 2 bytes so therefore we have the characters at index 0, 2, 4, 6 and 8
        System.out.println(Character.toString(inputByteBuffer.getChar(0)) + Character.toString(inputByteBuffer.getChar(2)) + Character.toString(inputByteBuffer.getChar(4)) + Character.toString(inputByteBuffer.getChar(6)) + Character.toString(inputByteBuffer.getChar(8)));
 
        // First int will be on index 10 because of the 2 bytes taken by the character before it
        System.out.println(inputByteBuffer.getInt(10));
 
        // Second int will be a at 14 because an int takes 4 bytes
        System.out.println(inputByteBuffer.getInt(14));
 
        // Third int will be a at 14 because an int takes 4 bytes
        System.out.println(inputByteBuffer.getInt(18));
 
        // Forth int will be a at 14 because an int takes 4 bytes
        System.out.println(inputByteBuffer.getInt(22));
 
        // Fifth int will be a at 14 because an int takes 4 bytes
        System.out.println(inputByteBuffer.getInt(26));
 
    }

// Json