What type of interface is used in the forEach method for processing collection elements?

In Java, the forEach method of collections uses the functional interface Consumer<T>. This interface contains a single abstract method accept(T t), which takes an element of the collection and performs some action with it.

Example of usage:

List<String> list = Arrays.asList("a", "b", "c");
list.forEach(item -> System.out.println(item));

Here, the lambda expression corresponds to the Consumer<String> interface, accepting each element and printing it.