Java Stream API Overview

The Java Stream API, introduced in Java 8, allows for functional-style operations on streams of elements. It provides a powerful and expressive way to process collections of data.

Key Concepts and Components

Stream

Description: A sequence of elements supporting sequential and parallel aggregate operations.

Creation:

• From Collections: stream(), parallelStream()
• From Arrays: Arrays.stream(array)
• From Other Sources: Stream.of(), Stream.generate(), Stream.iterate()

Intermediate Operations

Description: Operations that transform a stream into another stream. These operations are lazy and do not get executed until a terminal operation is performed.

Examples:

• filter(Predicate<? super T> predicate)
• map(Function<? super T, ? extends R> mapper)
• flatMap(Function<? super T, ? extends Stream<? extends R>> mapper)
• distinct()
• sorted()
• peek(Consumer<? super T> action)
• limit(long maxSize)
• skip(long n)

Terminal Operations

Description: Operations that produce a result or a side-effect. These operations trigger the processing of the stream pipeline.

Examples:

• forEach(Consumer<? super T> action)
• collect(Collector<? super T, A, R> collector)
• reduce(BinaryOperator<T> accumulator)
• toArray()
• min(Comparator<? super T> comparator)
• max(Comparator<? super T> comparator)
• count()
• anyMatch(Predicate<? super T> predicate)
• allMatch(Predicate<? super T> predicate)
• noneMatch(Predicate<? super T> predicate)
• findFirst()
• findAny()

Collectors

Description: Utility class providing implementations of various reduction operations, such as accumulating elements into collections, summarizing elements according to various criteria, etc.

Examples:

• Collectors.toList()
• Collectors.toSet()
• Collectors.toMap(Function<? super T, ? extends K> keyMapper, Function<? super T, ? extends U> valueMapper)
• Collectors.groupingBy(Function<? super T, ? extends K> classifier)
• Collectors.partitioningBy(Predicate<? super T> predicate)
• Collectors.joining(CharSequence delimiter)

Parallel Streams

Description: A parallel stream divides the content into multiple chunks and processes each chunk with a different thread.

Creation:

• From Collections: parallelStream()
• From Streams: stream().parallel()

Exception Handling in Streams

Description: Best practices for handling exceptions within streams, such as using wrappers and rethrowing exceptions.# Java-Stream-API