CN1-Stream

A lightweight Stream API from Java 8 rewritten on iterators for Codename One. Adapted from LSA, refactored, and cleaned up for CN1 compatibility.

Includes

• Functional interfaces (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.

Usage

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)...

Key features

Custom operators

Unlike Java 8 streams, CN1-Stream 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());
    }
}

Additional operators

In addition to back-ported Java 8 Stream operators, the library provides:

• filterNot - negated filter operator

  // Java 8
  stream.filter(((Predicate<String>) String::isEmpty).negate())
  // CN1-Stream
  stream.filterNot(String::isEmpty)

• select - filters instances of the given class

  // Java 8
  stream.filter(Integer.class::isInstance)
  // CN1-Stream
  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))
  // CN1-Stream
  stream.sortBy(Person::getName)

• groupBy - groups by extractor function

  // Java 8
  stream.collect(Collectors.groupingBy(Person::getName)).entrySet().stream()
  // CN1-Stream
  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]

• mapMulti / mapMultiToInt / mapMultiToLong / mapMultiToDouble - applies a mapper function to each element for producing replacing elements

  Stream.of(1, 2, 3, 4)
      .mapMulti((a, consumer) -> {
          consumer.accept(a); // value
          consumer.accept(-a); // negated value
          if (a % 2 == 0) {
             consumer.accept(a * 2); // multiply even value by 2
          }
      }) // [1, -1, 2, -2, 4, 3, -3, 4, -4, 8]

Throwable functions

No more ugly try/catch in lambda expressions.

// Java 8
stream.map(file -> {
    try {
        return new FileInputStream(file);
    } catch (IOException ioe) {
        return null;
    }
})
// CN1-Stream
stream.map(Function.Util.safe(FileInputStream::new))

JavaDocs

View the project JavaDoc

Download

Download latest release into your lib folder, or grab via CN1 Extensions Library in Codename One Control Center.

Do Refresh Libs after downloading.

Contribution

You are welcomed to improve the code.

• Fork the project
• commit your code
• create a pull request.

You can also improve the documentation, methods, and classes used.

Author

Diamond Dev Group.

License

MIT License

Copyright (c) 2021 Diamond Dev Group

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.