The Java Developers Almanac 1.4


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Home > List of Packages > java.nio  [27 examples] > Byte Buffers  [8 examples]

e160. Putting Bytes into a ByteBuffer

A ByteBuffer has a capacity which determines how many bytes it contains. This capacity can never change. Any byte in the ByteBuffer can be modified using the absolute version of put(), which takes an index in the range [0..capacity-1].

The bytes in a ByteBuffer can also be set using the relative version of put(), which uses the position and limit properties of the buffer. In particular, this version of put() sets the byte at the position and advances the position by one. put() cannot set bytes past the limit (even though limit might be less than the capacity). The position is always <= limit and limit is always <= capacity.

    // Create an empty ByteBuffer with a 10 byte capacity
    ByteBuffer bbuf = ByteBuffer.allocate(10);
    
    // Get the buffer's capacity
    int capacity = bbuf.capacity(); // 10
    
    // Use the absolute put().
    // This method does not affect the position.
    bbuf.put((byte)0xFF); // position=0
    
    // Set the position
    bbuf.position(5);
    
    // Use the relative put()
    bbuf.put((byte)0xFF);
    
    // Get the new position
    int pos = bbuf.position(); // 6
    
    // Get remaining byte count
    int rem = bbuf.remaining(); // 4
    
    // Set the limit
    bbuf.limit(7); // remaining=1
    
    // This convenience method sets the position to 0
    bbuf.rewind(); // remaining=7

 Related Examples
e158. Creating a ByteBuffer
e159. Getting Bytes from a ByteBuffer
e161. Converting Between a ByteBuffer an a Byte Array
e162. Getting and Setting Non-Byte Java Types in a ByteBuffer
e163. Creating a Non-Byte Java Type Buffer on a ByteBuffer
e164. Using a ByteBuffer to Store Strings
e165. Setting the Byte Ordering for a ByteBuffer

See also: File Locking    Files    Sockets    Streams   


© 2002 Addison-Wesley.