Mark and Reset

Like input streams, buffers can be marked and reset using the mark( ) and reset( ) methods:

public final Buffer mark( )
public final Buffer reset( ) throws InvalidMarkException

Initially, the mark is unset. Invoking the buffer's mark( ) method places the mark at the buffer's current position. Resetting returns the position to the previous mark. Unlike with InputStream, there's no markSupported( ) method. All buffers support marking and resetting.

The mark is always less than or equal to the position and the limit. If either the limit or the position is set to a value less than the current mark, the mark is cleared. Resetting when there's no mark throws an InvalidMarkException.