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While doing stream operations, during the intermediate/pipeline operations the streams would be created with different characteristics(e.g: SORTED/SIZED/DISTINCT/ORDERED) - Mastering Lambdas(Ch 6)
Stream.of(8,3,5,6,7,4) // ORDERED, SIZED
.filter(i->i%2==0) // ORDERED
.sorted() // ORDERED, SORTED
.distinct() // DISTINCT, ORDERED, SORTED
.map(i->i+1) // ORDERED
.unordered(); // none
How do we find out the different characteristics of the stream as mentioned in the above snippet?
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Introduced in Java 8, the Stream API is used to process collections of objects. A stream is a sequence of objects that supports various methods which can be pipelined to produce the desired result. A stream is not a data structure instead it takes input from the Collections, Arrays or I/O channels.
Java 8 offers the possibility to create streams out of three primitive types: int, long and double. As Stream<T> is a generic interface, and there is no way to use primitives as a type parameter with generics, three new special interfaces were created: IntStream, LongStream, DoubleStream.
Java Streams are basically a pipeline of aggregate operations that can be applied to process a sequence of elements. An aggregate operation is a higher-order function that receives a behaviour in a form of a function or lambda, and that behaviour is what gets applied to our sequence.
distinct() returns a stream consisting of distinct elements in a stream. distinct() is the method of Stream interface. This method uses hashCode() and equals() methods to get distinct elements. In case of ordered streams, the selection of distinct elements is stable.
At each stage you can call:
int c = stream.spliterator().characteristics();
And then test the result against the constants defined in the Spliterator class. For example to see if the stream is ordered:
boolean isOrdered = (c & Spliterator.ORDERED) == Spliterator.ORDERED;
Alternatively you can use:
boolean isOrdered = stream.spliterator().hasCharacteristics(Spliterator.ORDERED);
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