ObjectStreams (LensKit 3.0-M2)

java.lang.Object
- org.lenskit.util.io.ObjectStreams

public final class ObjectStreams
extends Object

Utility methods for streams.

Compatibility: Public

Method Summary

All Methods Static Methods Concrete Methods
Modifier and Type	Method and Description
`static <T> ObjectStream<T>`	`concat(Iterable<? extends ObjectStream<? extends T>> streams)` Concatenate object streams.
`static <T> ObjectStream<T>`	`concat(ObjectStream<? extends T>... objectStreams)` Concatenate object streams.
`static <T> ObjectStream<T>`	`consume(int n, ObjectStream<T> stream)` Consume and discard the first `n` elements from an object stream.
`static int`	`count(ObjectStream<?> objectStream)` Count the items in a stream.
`static <T> ObjectStream<T>`	`empty()` Create an empty object stream.
`static <T> ObjectStream<T>`	`filter(ObjectStream<?> stream, Class<T> type)` Filter an object stream to only contain elements of type `type`.
`static <T> ObjectStream<T>`	`filter(ObjectStream<T> stream, Predicate<? super T> predicate)` Filter an object stream.
`static <T> List<T>`	`makeList(ObjectStream<? extends T> objectStream)` Read an object stream into a list, closing when it is finished.
`static <T> ObjectStream<T>`	`of(T... contents)` Create an object stream over a fixed set of elements.
`static <T> ObjectStream<T>`	`sort(ObjectStream<T> objectStream, Comparator<? super T> comp)` Sort an object stream.
`static <S,T> ObjectStream<T>`	`transform(ObjectStream<S> objectStream, Function<? super S,? extends T> function)` Transform an object stream’s values.
`static <T> ObjectStream<T>`	`wrap(Collection<? extends T> collection)` Wrap a collection in an object stream.
`static <T> ObjectStream<T>`	`wrap(Iterator<? extends T> iterator)` Wrap an iterator in an object stream.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Method Detail
  - wrap
```
public static <T> ObjectStream<T> wrap(Iterator<? extends T> iterator)
```
    Wrap an iterator in an object stream.
    The iterator may not contain null. This property is checked lazily; the object stream will not fail until the null would be returned.
    
    Parameters:
    
    T - The type of data to return.
    
    iterator - An iterator to wrap
    
    Returns:
    
    An object stream returning the elements of the iterator.
  - wrap
```
public static <T> ObjectStream<T> wrap(Collection<? extends T> collection)
```
    Wrap a collection in an object stream.
    The iterator may not contain null. This property is checked lazily; the object stream will not fail until the null would be returned.
    
    Parameters:
    
    T - The type of data to return.
    
    collection - A collection to wrap
    
    Returns:
    
    An object stream returning the elements of the collection.
  - filter
```
public static <T> ObjectStream<T> filter(@WillCloseWhenClosed
                                         ObjectStream<T> stream,
                                         Predicate<? super T> predicate)
```
    Filter an object stream.
    
    Parameters:
    
    T - The type of object stream rows.
    
    stream - The source stream.
    
    predicate - A predicate indicating which rows to return.
    
    Returns:
    
    An object stream returning all rows for which predicate returns true.
  - filter
```
public static <T> ObjectStream<T> filter(@WillCloseWhenClosed
                                         ObjectStream<?> stream,
                                         Class<T> type)
```
    Filter an object stream to only contain elements of type type. Unlike filter(ObjectStream, Predicate) with a predicate from Predicates.instanceOf(Class), this method also transforms the stream to be of the target type.
    
    Parameters:
    
    T - The type of value in the stream.
    
    stream - The source stream.
    
    type - The type to filter.
    
    Returns:
    
    An object stream returning all elements in stream which are instances of type type.
  - consume
```
public static <T> ObjectStream<T> consume(int n,
                                          ObjectStream<T> stream)
```
    Consume and discard the first n elements from an object stream.
    
    Parameters:
    
    n - The number of elements to drop.
    
    stream - The stream.
    
    T - The stream’s element type.
    
    Returns:
    
    The passed-in stream, for convenience and functional-looking code. This method immediately consumes the elements, however, so stream is modified.
  - transform
```
public static <S,T> ObjectStream<T> transform(@WillCloseWhenClosed
                                              ObjectStream<S> objectStream,
                                              Function<? super S,? extends T> function)
```
    Transform an object stream’s values.
    
    Parameters:
    
    S - The type of source stream rows
    
    T - The type of output stream rows
    
    objectStream - The source stream
    
    function - A function to apply to each row in the stream. It will be applied to each value at most once.
    
    Returns:
    
    A new stream iterating the results of function.
  - empty
```
public static <T> ObjectStream<T> empty()
```
    Create an empty object stream.
    
    Parameters:
    
    T - The type of value in the object stream.
    
    Returns:
    
    An empty object stream.
  - makeList
```
public static <T> List<T> makeList(@WillClose
                                   ObjectStream<? extends T> objectStream)
```
    Read an object stream into a list, closing when it is finished.
    
    Parameters:
    
    T - The type of item in the object stream.
    
    objectStream - The object stream.
    
    Returns:
    
    A new list containing the elements of the object stream.
  - count
```
public static int count(@WillClose
                        ObjectStream<?> objectStream)
```
    Count the items in a stream.
    
    Parameters:
    
    objectStream - The object stream.
    
    Returns:
    
    The number of items in the stream.
  - sort
```
public static <T> ObjectStream<T> sort(@WillClose
                                       ObjectStream<T> objectStream,
                                       Comparator<? super T> comp)
```
    Sort an object stream. This reads the original object stream into a list, sorts it, and returns a new object stream backed by the list (after closing the original object stream).
    
    Parameters:
    
    T - The type of value in the object stream.
    
    objectStream - The object stream to sort.
    
    comp - The comparator to use to sort the object stream.
    
    Returns:
    
    An object stream iterating over the sorted results.
  - of
```
@SafeVarargs
public static <T> ObjectStream<T> of(T... contents)
```
    Create an object stream over a fixed set of elements. This is mostly useful for testing.
    
    Parameters:
    
    contents - The contents.
    
    T - The data type.
    
    Returns:
    
    The object stream.
  - concat
```
public static <T> ObjectStream<T> concat(Iterable<? extends ObjectStream<? extends T>> streams)
```
    Concatenate object streams. Each object stream is closed as closed as it is consumed.
    
    Parameters:
    
    streams - The object streams to concatenate.
    
    T - The type of data.
    
    Returns:
    
    The concatenated object stream.
  - concat
```
@SafeVarargs
public static <T> ObjectStream<T> concat(ObjectStream<? extends T>... objectStreams)
```
    Concatenate object streams.
    
    See Also:
    
    concat(Iterable)

Class ObjectStreams

Method Summary

Methods inherited from class java.lang.Object

Method Detail

wrap

wrap

filter

filter

consume

transform

empty

makeList

count

sort

of

concat

concat