Lambda expressions - Java 8 in Action: Lambdas, Streams, and Functional-Style Programming - page 65

Table 3.3. Examples of lambdas with functional interfaces

Use case Example of lambda Matching functional interface

A boolean (List<String> list) -> list.isEmpty() Predicate<List<String>>

expression

Creating objects () -> new Apple(10) Supplier<Apple>

Consuming from (Apple a) -> Consumer<Apple>

an object System.out.println(a.getWeight())

Select/extract (String s) -> s.length() Function<String, Integer> or

from an object ToIntFunction<String>

Combine two (int a, int b) -> a * b IntBinaryOperator

values

Compare two (Apple a1, Apple a2) -> Comparator<Apple> or

objects a1.getWeight().compareTo BiFunction<Apple, Apple, Integer> or

(a2.getWeight()) ToIntBiFunction<Apple, Apple>

What about exceptions, lambdas, and functional interfaces?

Note that none of the functional interfaces allow for a checked exception to be thrown. You have
two options if you need a lambda expression to throw an exception: define your own functional
interface that declares the checked exception, or wrap the lambda with a try/catch block.

For example, in section 3.3 we introduced a new functional interface Buffered-ReaderProcessor
that explicitly declared an IOException:

@FunctionalInterface
public interface BufferedReaderProcessor {
String process(BufferedReader b) throws IOException;

}
BufferedReaderProcessor p = (BufferedReader br) -> br.readLine();