java-8-functional-utils

java-8-functional-utils is a library that offers various enhancements for funtional programming in Java 8.

This is mainly an experimental project and shouldn't be considered robust enough for critical applications.

RichStream

RichStream is the core of the enhancements provided by this library. A RichStream can be created from a stream, a collection, an array, or an iterator:

RichStream.of(stream);
RichStream.of(list.stream());

RichStream has all the same methods as Java's built-in Stream class, with the exception that when appropriate they will return a RichStream instead of a Stream.

However, RichStream has several enhancements as well.

filterNot

filterNot is a quick way of negating the results of filter. Similar to filter, it takes a Predicate, but keeps only elements that do not match it.

zip and zipWithIndex

zip combines two streams into a single stream pairing elements from the two original streams. The resulting stream has the same length as the shorter of the two original streams.

zipWithIndex pairs each element of the stream with its index, starting from 0.

Neither method is recommended for use with infinite streams.

Collection Conversions

RichStream offers several shortcuts for terminally transforming a stream into a collection:

1. toList: Turns the stream into a List
2. toSet: Turns the stream into a Set
3. toMapAsKey: Turns the stream into a Map with the stream elements as keys, applying a Function to produce the values
4. toMapAsValue: Turns the stream into a Map with the stream elements as values, applying a Function to produce the keys
5. toMap: Turns the stream into a Map, applying one Function to produce the keys and another to produce the values

Checked Exceptions in Lambdas

Java 8's lambda expressions do not support checked exceptions. As such they must be rewritten to avoid them or catch and rethrow an unchecked exception.

This project adds a ConsumerWithCheckedException, FunctionWithCheckedException, PredicateWithCheckedException and some primitive specializations thereof to support lambdas that do allow for checked exceptions. Methods on RichStream like map or filter then take either the built-in version without checked exceptions or these new implementations.