Java 11: Understanding Stream Operations

In Java, Stream operations can be classified into two categories: intermediate operations and terminal operations. Below is a list of some of the most common Stream operations in Java 11, along with a brief description of each.

Intermediate Operations

• filter(Predicate predicate): Filters the Stream's elements based on the given predicate and returns a new Stream containing only the elements that meet the predicate's condition.
• map(Function mapper): Applies the given mapping function to each element of the Stream and returns a new Stream with the resulting elements.
• flatMap(Function> mapper): Applies the given mapping function to each element of the Stream and "flattens" the result into a new Stream. Useful for combining multiple Streams into a single one.
• distinct(): Returns a new Stream containing only distinct elements based on their natural equality comparison.
• sorted(): Returns a new Stream containing the elements sorted according to their natural order.
• sorted(Comparator comparator): Returns a new Stream containing the elements sorted according to the provided comparator.
• peek(Consumer action): Performs an action on each element of the Stream as they pass by, typically used for debugging or performing side effects. Returns a new Stream containing the same elements.

Terminal Operations

• forEach(Consumer action): Performs an action for each element of the Stream. Does not return any result.
• toArray(): Converts the Stream into an array containing all its elements.
• reduce(BinaryOperator accumulator): Iteratively applies an accumulator function to the Stream's elements, and returns an Optional with the accumulated result.
• collect(Collector collector): Performs a mutable reduction on the Stream's elements using a Collector, and returns the result.
• min(Comparator comparator): Finds and returns the minimum element of the Stream according to the provided comparator.
• max(Comparator comparator): Finds and returns the maximum element of the Stream according to the provided comparator.
• count(): Counts the number of elements in the Stream and returns the result.
• anyMatch(Predicate predicate): Checks if any element of the Stream meets the condition of the given predicate.
• allMatch(Predicate predicate): Checks if all elements of the Stream meet the condition of the given predicate.