forEachRemaining

ForEachRemaining is a method provided by Java's iteration interfaces that applies a given action to each element that has not yet been visited by an iterator or spliterator. It processes the remaining elements in the order of traversal, avoiding an explicit loop in user code.

In Java 8, forEachRemaining is defined as a default method on the Iterator interface with the signature void forEachRemaining(Consumer<? super E> action). There is a corresponding method in the Spliterator interface, public void forEachRemaining(Consumer<? super T> action). Both take a Consumer that defines the operation to perform on each element.

Behavior: The action is applied to each remaining element until all have been processed. If action is null, a NullPointerException is thrown. If the consumer throws an exception, it propagates to the caller. Modifying the underlying data structure during iteration in ways that affect the iteration may lead to unspecified behavior or exceptions.

Usage notes: Some implementations may provide optimized implementations for performance. Implementations may allow certain modifications via the iterator’s remove method during processing. It is generally used for side effects such as logging, updating external state, or triggering computations; it does not produce a return value.

See also: Iterator, Spliterator, java.util.function.Consumer.