Module java.base
Package java.nio.channels

# Interface CompletionHandler<V,A>

Type Parameters:
  `V` - The result type of the I/O operation
  `A` - The type of the object attached to the I/O operation

public interface CompletionHandler<V,A>
A handler for consuming the result of an asynchronous I/O operation.

The asynchronous channels defined in this package allow a completion handler to be specified to consume the result of an asynchronous operation. The `completed` method is invoked when the I/O operation completes successfully. The `failed` method is invoked if the I/O operations fails. The implementations of these methods should complete in a timely manner so as to avoid keeping the invoking thread from dispatching to other completion handlers.

Since:
  1.7

## Method Summary

Modifier and Type
Method
Description
`void`
`completed(V result, A attachment)`
Invoked when an operation has completed.
`void`
`failed(Throwable exc, A attachment)`
Invoked when an operation fails.

## Method Details

### completed

void completed(V result, A attachment)
Invoked when an operation has completed.

Parameters:
  `result` - The result of the I/O operation.
  `attachment` - The object attached to the I/O operation when it was initiated.

### failed

void failed(Throwable exc, A attachment)
Invoked when an operation fails.

Parameters:
  `exc` - The exception to indicate why the I/O operation failed
  `attachment` - The object attached to the I/O operation when it was initiated.