java类库详细讲解

				
				
				
				Putting Bytes into a ByteBuffer
				(Java Developers Almanac Example)
				
				
				
				
				
				
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				The Java Developers Almanac 1.4
				
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				    java.nio
				         [27 examples]
				        
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				        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.