difference between bytebuffer.flip() and bytebuffer.rewind()

Question

I am aware that flip() set the current buffer position to 0 and set the limit to the previous buffer position whereas rewind() just set the current buffer position to 0.

In the following code, either I use rewind() or flip() i get the same result.

byte b = 127; bb.put(b); bb.rewind();//or flip();  System.out.println(bb.get()); bb.rewind();// or flip(); System.out.println(bb.get()); 

Could you provide me with a real example where the difference of these 2 methods really matters? Thanks in advance.

Answer 1

From the source code, they are very similar. You can see the follow:

public final Buffer flip() {     limit = position;     position = 0;     mark = -1;     return this; }  public final Buffer rewind() {     position = 0;     mark = -1;     return this; } 

So the difference is the flip set the limit to the position, while rewind not. Consider you have allocated a buffer with 8 bytes, you have filled the buffer with 4 bytes, then the position is set to 3, just show as follow:

    [ 1  1  1  1  0  0  0  0]                |           | flip           limit       | rewind                     limit 

So rewind just used limit has set appropriately.

Answer 2

They're not equivalent at all.

A ByteBuffer is normally ready for read() (or for put()).

flip() makes it ready for write() (or for get()).

rewind() and compact() and clear() make it ready for read()/put() again after write() (or get()).