OptionalChainingComposed.java

public class OptionalChainingComposed {

    public static void main(String[] args) {
        OptionalChainingComposed optionalChaining = new OptionalChainingComposed();
        optionalChaining.happyPath();
        optionalChaining.nullInput();
    }

    public void happyPath() {
        nonNullPipeline("happyPath")
                .ifPresent(System.out::println);
    }

    public void nullInput() {
        nonNullPipeline(null).ifPresent(val -> val.concat("boom!"));
    }


    // Instead of THIS:
//    public Optional<String> nonNullPipeline(String string) {
//        return Optional.ofNullable(stringOptional)
//                .map(val -> operation1.apply(val))
//                .map(val -> operation2.apply(val))
//                .map(val -> operation3.apply(val));
//    }

    // put these here so we don't get an illegal forward reference...
    Function<String, String> operation1 = String::toLowerCase;
    Function<String, String> operation2 = String::toUpperCase;
    Function<String, String> operation3 = value -> value.concat("suffix");
    Function<String, String> operation4 = value -> null;

    // We can do THIS:
    Function<String, String> pipelineOne = operation1.andThen(operation2).andThen(operation3);

    // And this:
    public Optional<String> nonNullPipeline(String string) {
        return Optional.ofNullable(string).map(pipelineOne);
    }

}