[JAVA] Exception handling with a fluid interface

Writing exception handling is always a hassle, so I arranged it a little.

Method that raises a checked exception

void raiseIOEx1(String s) throws IOException {
    if (s.equals("nagare")) {
        System.out.println("Excellent!");
        return;
    }
    throw new IOException("invalid input :".concat(s));
}

It's a rough idea, but when there is a method like the one above (aside from why IOException?)

Normal writing

void usually_try_style() {
    try {
        raiseIOEx1("nagare");
    } catch (IOException e) {
        e.printStackTrace();
    }
}

Arranged writing style

void nagare_try_style() {
    Try.throwable(this::raiseIOEx1)
            .ifCatch(IOException::printStackTrace)
            .accept("nagare");
}

You can write like this.

Also, in the case of a method that returns a value, you can write as follows.

Method 2 that raises a checked exception

String raiseIOEx2(String s) throws IOException {
    if (s.equals("nagare")) {
        return "Excellent!";
    }
    throw new IOException("invalid input :".concat(s));
}

Normal writing

void usually_returnable_try_style() {
    try {
        String s = raiseIOEx2("nagare");
        System.out.println(s);
    } catch (IOException e) {
        e.printStackTrace();
    }
}

Arranged writing style

void nagare_returnable_try_style() {
    Optional<String> s = Try.throwable(this::raiseIOEx2)
            .ifCatch(IOException::printStackTrace)
            .apply("nagare");
    s.ifPresent(System.out::println);

    // or
    Try.throwable(this::raiseIOEx2)
            .ifCatch(IOException::printStackTrace)
            .apply("nagare");
            .ifPresent(System.out::println);
}

It is not recommended to use it at the business level, but the above description can be made by adding the following 4 classes.

public class Try {
    public static <X, A, E extends Exception> ThrowableFunc<X, A, E> throwable(
            ThrowableFunc<X, A, E> f) {
        return f;
    }

    public static <X, E extends Exception> ThrowableSpender<X, E> throwable(
            ThrowableSpender<X, E> s) {
        return s;
    }
}

@FunctionalInterface
public interface ThrowableSpender<X, E extends Exception> {
    void accept(X x) throws E;

    default Consumer<X> ifCatch(ExHandler<E> handler) {
        return (X x) -> {
            try {
                accept(x);
            } catch (Exception e) {
                @SuppressWarnings("unchecked")
                E typedE = (E) e; // is type safe
                handler.handle(typedE);
            }
        };
    }
}

@FunctionalInterface
public interface ThrowableFunc<X, A, E extends Exception> {
    A apply(X x) throws E;

    default Function<X, Optional<A>> ifCatch(ExHandler<E> handler) {
        return x -> {
            try {
                return Optional.of(apply(x));
            } catch (Exception e) {
                @SuppressWarnings("unchecked")
                E typedE = (E) e; // is type safe
                handler.handle(typedE);
            }
            return Optional.empty();
        };
    }
}

@FunctionalInterface
public interface ExHandler<E extends Exception> {
    void handle(E e);
}

As you can see by reading the code, I'm a little cheating at catch.

try {
    accept(x);
} catch (E e) {
    handler.handle(e);
}

If you can write like this, you will be able to write multiple exceptions only with the interface, which seems to make a lot of progress, but it's a shame. I hope you can write in java9.

https://github.com/mt-village/nagare

reference

-How to handle exceptions coolly with Stream and Optional of Java8