# Package org.apache.storm.streams.operations

- Interface Summary
  Interface | Description
  --- | ---
  BiFunction<T,​U,​R> | a function that accepts two arguments and produces a result.
  CombinerAggregator<T,​A,​R> | Interface for aggregating values.
  Consumer<T> | Represents an operation that accepts a single input argument and returns no result.
  FlatMapFunction<T,​R> | A function that accepts one argument and returns an `Iterable` of elements as its result.
  Function<T,​R> | Represents a function that accepts one argument and produces a result.
  Operation | The parent interface for any kind of streaming operation.
  PairFlatMapFunction<T,​K,​V> | A function that accepts one argument and returns an `Iterable` of `Pair` as its result.
  PairFunction<T,​K,​V> | A function that accepts an argument and produces a key-value Pair.
  Predicate<T> | Represents a predicate (boolean-valued function) of a value.
  Reducer<T> | The `Reducer` performs an operation on two values of the same type producing a result of the same type.
  StateUpdater<T,​S> | Interface for updating state.
  ValueJoiner<V1,​V2,​R> | An interface for joining two values to produce a result.

- Class Summary
  Class | Description
  --- | ---
  IdentityFunction<T> | A `Function` that returns the input argument itself as the result.
  PairValueJoiner<V1,​V2> | A `ValueJoiner` that joins two values to produce a `Pair` of the two values as the result.
  PrintConsumer<T> | A consumer that prints the input to stdout.