com.metamx.common.guava.Sequence Maven / Gradle / Ivy
/*
* Copyright 2011,2012 Metamarkets Group Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.metamx.common.guava;
/**
* A Sequence represents an iterable sequence of elements. Unlike normal Iterators however, it doesn't expose
* a way for you to extract values from it, instead you provide it with a worker (an Accumulator) and that defines
* what happens with the data.
*
* This inversion of control is in place to allow the Sequence to do resource management. It can enforce that close()
* methods get called and other resources get cleaned up whenever processing is complete. Without this inversion
* it is very easy to unintentionally leak resources when iterating over something that is backed by a resource.
*
* Sequences also expose {#see com.metamx.common.guava.Yielder} Yielder objects which allow you to implement a
* continuation over the Sequence. Yielder do not offer the same guarantees of automagic resource management
* as the accumulate method, but they are Closeable and will do the proper cleanup when close() is called on them.
*/
public interface Sequence
{
public OutType accumulate(OutType initValue, Accumulator accumulator);
public Yielder toYielder(OutType initValue, YieldingAccumulator accumulator);
}