io.druid.java.util.common.guava

Interface Yielder<T>

All Superinterfaces:

AutoCloseable, Closeable

All Known Implementing Classes:

ExecuteWhenDoneYielder

public interface Yielder<T>
extends Closeable

A Yielder is an object that tries to act like the yield() command/continuations in other languages. It's not necessarily good at this job, but it works. I think. Essentially, you can think of a Yielder as a linked list of items where the Yielder gives you access to the current head via get() and it will give you another Yielder representing the next item in the chain via next(). A Yielder that isDone() may return anything from both get() and next(), there is no contract and depending on those return values will likely lead to bugs. Once next is called, there is no guarantee and no requirement that references to old Yielder objects will continue to obey the contract. Yielders are Closeable and *must* be closed in order to prevent resource leaks. Once close() is called, the behavior of the whole chain of Yielders is undefined.

Method Summary

Modifier and Type	Method and Description
T	get() Gets the object currently held by this Yielder.
boolean	isDone() Returns true if this is the last Yielder in the chain.
Yielder<T>	next(T initValue) Gets the next Yielder in the chain.

Methods inherited from interface java.io.Closeable

close

Method Detail

get

T get()

Gets the object currently held by this Yielder. Can be called multiple times as long as next() is not called. Once next() is called on this Yielder object, all further operations on this object are undefined.

Returns:

the currently yielded object, null if done

next

Yielder<T> next(T initValue)

Gets the next Yielder in the chain. The argument is used as the accumulator value to pass along to start the accumulation until the next yield() call or iteration completes. Once next() is called on this Yielder object, all further operations on this object are undefined.

Parameters:

initValue - the initial value to pass along to start the accumulation until the next yield() call or iteration completes.

Returns:

the next Yielder in the chain, or undefined if done

isDone

boolean isDone()

Returns true if this is the last Yielder in the chain. A Yielder that isDone() may return anything from both get() and next(), there is no contract and depending on those return values will likely lead to bugs. It will probably break your code to call next() on a Yielder that is done and expect something good from it. Once next() is called on this Yielder object, all further operations on this object are undefined.

Returns:

true if this is the last Yielder in the chain, false otherwise