Stream API from Java 8 rewritten on iterators for Java 7 and below.
Supplier, Function, Consumer etc);Stream/IntStream/LongStream/DoubleStream (without parallel processing, but with a variety of additional methods and with custom operators);Optional/OptionalBoolean/OptionalInt/OptionalLong/OptionalDouble classes;Exceptional class - functional way to deal with exceptions;Objects from Java 7.Stream.of(/* array | list | set | map | anything based on Iterator/Iterable interface */)
.filter(..)
.map(..)
...
.sorted()
.forEach(..);
Stream.of(value1, value2, value3)...
IntStream.range(0, 10)...Example project: https://github.com/aNNiMON/Android-Java-8-Stream-Example
Unlike Java 8 streams, Lightweight-Stream-API provides the ability to apply custom operators.
Stream.of(...)
.custom(new Reverse<>())
.forEach(...);
public final class Reverse<T> implements UnaryOperator<Stream<T>> {
@Override
public Stream<T> apply(Stream<T> stream) {
final Iterator<? extends T> iterator = stream.getIterator();
final ArrayDeque<T> deque = new ArrayDeque<T>();
while (iterator.hasNext()) {
deque.addFirst(iterator.next());
}
return Stream.of(deque.iterator());
}
}You can find more examples here.
In addition to backported Java 8 Stream operators, the library provides:
filterNot - negated filter operator
// Java 8
stream.filter(((Predicate<String>) String::isEmpty).negate())
// LSA
stream.filterNot(String::isEmpty)select - filters instances of the given class
// Java 8
stream.filter(Integer.class::isInstance)
// LSA
stream.select(Integer.class)withoutNulls - filters only not null elements
Stream.of("a", null, "c", "d", null)
.withoutNulls() // [a, c, d]sortBy - sorts by extractor function
// Java 8
stream.sorted(Comparator.comparing(Person::getName))
// LSA
stream.sortBy(Person::getName)groupBy - groups by extractor function
// Java 8
stream.collect(Collectors.groupingBy(Person::getName)).entrySet().stream()
// LSA
stream.groupBy(Person::getName)chunkBy - partitions sorted stream by classifier function
Stream.of("a", "b", "cd", "ef", "gh", "ij", "klmnn")
.chunkBy(String::length) // [[a, b], [cd, ef, gh, ij], [klmnn]]sample - emits every n-th elements
Stream.rangeClosed(0, 10)
.sample(2) // [0, 2, 4, 6, 8, 10]slidingWindow - partitions stream into fixed-sized list and sliding over the elements
Stream.rangeClosed(0, 10)
.slidingWindow(4, 6) // [[0, 1, 2, 3], [6, 7, 8, 9]]takeWhile / dropWhile - introduced in Java 9, limits/skips stream by predicate function
Stream.of("a", "b", "cd", "ef", "g")
.takeWhile(s -> s.length() == 1) // [a, b]
Stream.of("a", "b", "cd", "ef", "g")
.dropWhile(s -> s.length() == 1) // [cd, ef, g]scan - iteratively applies accumulation function and returns Stream
IntStream.range(1, 6)
.scan((a, b) -> a + b) // [1, 3, 6, 10, 15]indexed - adds an index to every element, result is IntPair
Stream.of("a", "b", "c")
.indexed() // [(0 : "a"), (1 : "b"), (2 : "c")]filterIndexed / mapIndexed / takeWhileIndexed / takeUntilIndexed / dropWhileIndexed / reduceIndexed / forEachIndexed - indexed specialization of operators
Stream.of("a", "b", "c")
.mapIndexed((i, s) -> s + Integer.toString(i)) // [a0, b1, c2]No more ugly try/catch in lambda expressions.
// Java 8
stream.map(file -> {
try {
return new FileInputStream(file);
} catch (IOException ioe) {
return null;
}
})
// LSA
stream.map(Function.Util.safe(FileInputStream::new))Download latest release or grab via Maven:
<dependency>
<groupId>com.annimon</groupId>
<artifactId>stream</artifactId>
<version>1.2.1</version>
</dependency>or Gradle:
dependencies {
...
implementation 'com.annimon:stream:1.2.1'
...
}or use latest unrealeased features with JitPack.
Also included version for Java ME. Checkout javame branch.