Stream
java.tuil.stream
Stream<T>
Stream Creation
Stream can be created with the help of stream() and of() method
Array
Stream<String> stream = Arrays.stream(array);
stream = Stream.of("a","b","c")
Collection
Stream<String> stream = list.stream();
Multi-threading with Streams
parallelStream() method
list.parallelstream().forEach(element -> doWork(element));
Stream Operations
Iterating
Substitute for, forEach, while loops. It allows concentrating on operation’s logic.
boolean isExist = list.stream().anyMatch(element -> element.contains("a"));
Filtering
filter() method allows us to pick stream of elements which satisfy a predicate
- Finds all elements of this stream which contain char “d”
- creates a new stream containing only the filtered elements
Stream<String> stream = list.stream().filter(element -> element.contains("d"));
Mapping
To validate elements of a sequence according to some predicate
- anyMatch()
- allMatch()
- noneMatch()
boolean isValid = list.stream().anyMatch(element -> elemnt.contains("1"));
boolean isValidOne = list.stream().allMatch(element -> elemnt.contains("1"));
boolean isValidnone = list.stream().noneMatch(element -> elemnt.contains("1"));
Reduction
Reduce a sequence of elements to some value according to a specified function with the help of the reduce()method of the type Stream
Integer reduced = integers.stream().reduce(23, (a, b) -> a + b);
Collecting
Reduction can also be provided by the collect() method of type Stream
It could be very handy in case of converting a stream to Collection or a Map
Collectors provide a solution for almost all typical collecting operation
Methods
sum()
Return sum of element in the stream
This is special case of Reduction
mapToInt
Return a int stream consisting of the results of applying the given function to the elements of this stream.
param : function to apply to each element
Return : new stream
