Streams

Streams implement the pipeline pattern, chaining operations into a single flow.

Some common uses are filtering and mapping:

final Collection<Wrapper> result;

result = strings.stream().filter(StringUtils::isNotBlank).map(Wrapper::new).collect(Collectors.toList());

Generation

Stream From Array

Stream<String> stream;

stream  = Stream.of("abc", "def");

Stream From Iterable

Iterables don't give support to streams by default, but there is a utility class for this:

Iterable<String> strings;
Stream<String> stream;

stream = StreamSupport.stream(strings.spliterator(), false);

Empty Stream

Stream<String> empty;

empty = Stream.empty();

From Supplier

Stream<String> stream;
Supplier<String> supplier;

supplier = this::operation;

stream = Stream.generate(supplier);

Builder

Stream<String> stream;
Supplier<String> supplier;

supplier = this::operation;

stream = Stream.builder().add("text").build();

Iteration

Stream<Integer> stream;

// Numbers 1 to 10
stream = Stream.iterate(1, n -> n).limit(10);

From Other Streams

Stream<String> stream;

stream = Stream.concat(streamA, streamB);

Closing Streams

In some cases the streams can be working with an IO data source, or some other source which should be closed after being used. For that reason streams extend the AutoCloseable interface.