org.apache.flink.api.common.functions

Class RichFoldFunction<O,T>

java.lang.Object

org.apache.flink.api.common.functions.AbstractRichFunction

org.apache.flink.api.common.functions.RichFoldFunction<O,T>

Type Parameters:

T - Type of the initial input and the returned element

O - Type of the elements that the group/list/stream contains

All Implemented Interfaces:

Serializable, FoldFunction<O,T>, Function, RichFunction

@Public
public abstract class RichFoldFunction<O,T>
extends AbstractRichFunction
implements FoldFunction<O,T>

Rich variant of the FoldFunction. As a RichFunction, it gives access to the RuntimeContext and provides setup and teardown methods: RichFunction.open(org.apache.flink.configuration.Configuration) and RichFunction.close().

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
RichFoldFunction()

Method Summary

Modifier and Type	Method and Description
abstract T	fold(T accumulator, O value) The core method of FoldFunction, combining two values into one value of the same type.

Methods inherited from class org.apache.flink.api.common.functions.AbstractRichFunction

close, getIterationRuntimeContext, getRuntimeContext, open, setRuntimeContext

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

RichFoldFunction

public RichFoldFunction()

Method Detail

fold

public abstract T fold(T accumulator,
                       O value)
                throws Exception

Description copied from interface: FoldFunction

The core method of FoldFunction, combining two values into one value of the same type. The fold function is consecutively applied to all values of a group until only a single value remains.

Specified by:

fold in interface FoldFunction<O,T>

Parameters:

accumulator - The initial value, and accumulator.

value - The value from the group to "fold" into the accumulator.

Returns:

The accumulator that is at the end of the "folding" the group.

Throws:

Exception - This method may throw exceptions. Throwing an exception will cause the operation to fail and may trigger recovery.