How to get a range of items from stream using Java 8 lambda?

by

To get a range from a Stream<T>, you can use skip(long n) to first skip a set number of elements, and then you can call limit(long n) to only take a specific amount of items.

Consider a stream with 10 elements, then to get elements 3 to 7, you would normally call from a List: 

list.subList(3, 7);

Now with a Stream, you need to first skip 3 items, and then take 7 – 3 = 4 items, so it becomes:

stream.skip(3).limit(4);

As a variant to @StuartMarks’ solution to the second answer, I’ll offer you the following solution which leaves the possibility to chain intact, it works similar to how @StuartMarks does it:

private <T> Collector<T, ?, Stream<T>> topPercentFromRangeCollector(Comparator<T> comparator, double from, double to) {
    return Collectors.collectingAndThen(
        Collectors.toList(),
        list -> list.stream()
            .sorted(comparator)
            .skip((long)(list.size() * from))
            .limit((long)(list.size() * (to - from)))
    );
}

and

IntStream.range(0, 100)
        .boxed()
        .collect(topPercentFromRangeCollector(Comparator.comparingInt(i -> i), 0.1d, 0.3d))
        .forEach(System.out::println);

This will print the elements 10 through 29.

It works by using a Collector<T, ?, Stream<T>> that takes in your elements from the stream, transforms them into a List<T>, then obtains a Stream<T>, sorts it and applies the (correct) bounds to it.

More Related Contents:

  1. Java 8 Streams: multiple filters vs. complex condition
  2. Get List<K> from HashMap<K, V> where V is instance of I [closed]
  3. What are functional interfaces used for in Java 8?
  4. Why filter() after flatMap() is “not completely” lazy in Java streams?
  5. How to force max to return ALL maximum values in a Java Stream?
  6. What is the equivalent lambda expression for System.out::println
  7. Copy a stream to avoid “stream has already been operated upon or closed”
  8. Does a lambda expression create an object on the heap every time it’s executed?
  9. Lambdas: local variables need final, instance variables don’t
  10. Precise definition of “functional interface” in Java 8
  11. Java 8: Difference between method reference Bound Receiver and UnBound Receiver
  12. Lambda expression vs method reference
  13. Java 8 Lambda Expressions – what about multiple methods in nested class
  14. _ (underscore) is a reserved keyword
  15. Lambda this reference in java
  16. java.lang.ClassCastException using lambda expressions in spark job on remote server
  17. Filter Java Stream to 1 and only 1 element
  18. Java 8: Where is TriFunction (and kin) in java.util.function? Or what is the alternative?
  19. Why do I need a functional Interface to work with lambdas?
  20. Find maximum, minimum, sum and average of a list in Java 8
  21. How do I use the new computeIfAbsent function?
  22. Java 8: Mandatory checked exceptions handling in lambda expressions. Why mandatory, not optional?
  23. Java access bean methods with LambdaMetafactory
  24. Java 8 Filter Array Using Lambda
  25. Lambdas in the classical Operation enum example
  26. Implied anonymous types inside lambdas
  27. Why does this Java 8 lambda fail to compile?
  28. FunctionalInterface Comparator has 2 abstract methods
  29. Stream.peek() method in Java 8 vs Java 9
  30. Java 8 stream map to list of keys sorted by values

Leave a Comment