OptionalChaining

public class OptionalChaining {
    public static void main(String[] args) {
        OptionalChaining optionalChaining = new OptionalChaining();
        optionalChaining.happyPath();
        optionalChaining.nullInput();
        optionalChaining.thereBeNullsHereOne();
        optionalChaining.thereBeNullsHereTwo();
    }

    // Happy path with a pipeline that doesn't return nulls
    public void happyPath() {
        nonNullPipeline("happyPath")
                .ifPresent(System.out::println);
    }

    // Pass in a null, no problem (and no null checks)
    public void nullInput() {
        nonNullPipeline(null).ifPresent(val -> val.concat("boom!"));
    }

    // Pipeline with a null response in the first unit
    public void thereBeNullsHereOne() {
        prefixNullPipeline("thereBeNullsHereOne")
                .ifPresent(System.out::println);
    }
    
    // Pipeline with a null response in the middle 
    public void thereBeNullsHereTwo() {
        randomNullPipeline("thereBeNullsHereTwo")
                .ifPresent(System.out::println);
    }

    public Optional<String> nonNullPipeline(String stringOptional) {
        return Optional.ofNullable(stringOptional)
                .map(val -> operation1.apply(val))
                .map(val -> operation2.apply(val))
                .map(val -> operation3.apply(val));
    }

    public Optional<String> prefixNullPipeline(String stringOptional) {
        return Optional.ofNullable(stringOptional)
                .map(val -> operation4.apply(val)) // Null returned here!!
                .map(val -> operation1.apply(val))
                .map(val -> operation2.apply(val))
                .map(val -> operation3.apply(val));
    }

    public Optional<String> randomNullPipeline(String stringOptional) {
        return Optional.ofNullable(stringOptional)
                .map(val -> operation1.apply(val))
                .map(val -> operation4.apply(val)) // Null returned here!!
                .map(val -> operation2.apply(val))
                .map(val -> operation3.apply(val));
    }

    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;
}