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

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.