Returns this selector's key set.

  Returns this selector's key set.

The key set is not directly modifiable. A key is removed only after it has been cancelled and its channel has been deregistered. Any attempt to modify the key set will cause an UnsupportedOperationException to be thrown.

The key set is not thread-safe.

Returns: This selector's key set
Throws:
- ClosedSelectorException - If this selector is closed

  Opens a selector.

  Opens a selector.

The new selector is created by invoking the openSelector method of the system-wide default SelectorProvider object.

Returns: A new selector
Throws:
- IOException - If an I/O error occurs

  Selects a set of keys whose corresponding channels are ready for I/O operations.

  Selects a set of keys whose corresponding channels are ready for I/O operations.

This method performs a blocking selection operation. It returns only after at least one channel is selected, this selector's wakeup method is invoked, or the current thread is interrupted, whichever comes first.

Returns: The number of keys, possibly zero, whose ready-operation sets were updated
Throws:
- IOException - If an I/O error occurs
- ClosedSelectorException - If this selector is closed

  Selects a set of keys whose corresponding channels are ready for I/O operations.

  Selects a set of keys whose corresponding channels are ready for I/O operations.

This method performs a blocking selection operation. It returns only after at least one channel is selected, this selector's wakeup method is invoked, the current thread is interrupted, or the given timeout period expires, whichever comes first.

This method does not offer real-time guarantees: It schedules the timeout as if by invoking the Object.wait(long) method.

Returns: The number of keys, possibly zero, whose ready-operation sets were updated
Parameters:
- timeout - If positive, block for up to timeout milliseconds, more or less, while waiting for a channel to become ready; if zero, block indefinitely; must not be negative
Throws:
- IOException - If an I/O error occurs
- ClosedSelectorException - If this selector is closed
- IllegalArgumentException - If the value of the timeout argument is negative

  Returns this selector's selected-key set.

  Returns this selector's selected-key set.

Keys may be removed from, but not directly added to, the selected-key set. Any attempt to add an object to the key set will cause an UnsupportedOperationException to be thrown.

The selected-key set is not thread-safe.

Returns: This selector's selected-key set
Throws:
- ClosedSelectorException - If this selector is closed

  Selects a set of keys whose corresponding channels are ready for I/O operations.

  Selects a set of keys whose corresponding channels are ready for I/O operations.

This method performs a non-blocking selection operation. If no channels have become selectable since the previous selection operation then this method immediately returns zero.

Invoking this method clears the effect of any previous invocations of the wakeup method.

Returns: The number of keys, possibly zero, whose ready-operation sets were updated by the selection operation
Throws:
- IOException - If an I/O error occurs
- ClosedSelectorException - If this selector is closed

  Causes the first selection operation that has not yet returned to return immediately.

  Causes the first selection operation that has not yet returned to return immediately.

If another thread is currently blocked in an invocation of the Selector.select() or Selector.select(long) methods then that invocation will return immediately. If no selection operation is currently in progress then the next invocation of one of these methods will return immediately unless the Selector.selectNow() method is invoked in the meantime. In any case the value returned by that invocation may be non-zero. Subsequent invocations of the Selector.select() or Selector.select(long) methods will block as usual unless this method is invoked again in the meantime.

Invoking this method more than once between two successive selection operations has the same effect as invoking it just once.

Returns: This selector