Understanding Stream API in Java Stream API is a feature introduced in Java 8 to process collections of data efficiently. Unlike traditional loops or forEach, streams allow operations like mapping, filtering, and reducing without altering the original collection. Streams are immutable and can only be consumed once during processing.
Creating Streams from Collections Streams can be created using the stream() method on collections such as lists. This generates a flow of values that allows various transformations while keeping the original list unchanged. Parallel streams enable multi-threaded processing managed by Java itself.
Mapping Values with Stream Map Method The map method transforms each element within a stream based on specified logic (e.g., doubling numbers). It creates new transformed streams rather than modifying existing ones, ensuring immutability throughout operations.
Filtering Data Using Predicates Filters apply conditions to elements within a stream using predicates—a functional interface returning true or false based on criteria (e.g., odd/even checks). Lambda expressions simplify predicate implementation for concise code writing.
'For Each' vs 'Reduce': Aggregating Results Efficiently 'For Each' iterates through all elements individually but does not aggregate results directly; Reduce combines them into single outcomes via binary operators starting at an initial value—ideal when summing up filtered/mapped datasets effectively