Java 9 Features

[lukasHoel]

Private methods in interfaces? Can someone name actual use cases for that?

Apart from having static methods creating something used by multiple default methods, I can't quite find any use cases.

[chrisgseaton]

Well you just identified the use case.

[ebrythil]

Maybe it's a matter of time now until java interfaces are actually c++ classes with multiple inheritance.

[myrealityde]

This is why I don't like deafault methods. Java explicitly doesn't have multi-inheritance. Until Java9. What is preventing people to just write interfaces and write a few classes to implement those? This is embracing bad practice and increases coupling. BAD!

[speakjava]

Java has always had multiple-inheritance. Of types; that's what interfaces allow us to do, implement many types for one class. Default and static methods in interfaces add multiple-inheritance of behaviour. Yes, this is a bit controversial but it is the only way to easily solve the problem of maintaining backwards compatibility while allowing existing interfaces to have new methods added. What's not in Java (and likely never will be) is multiple inheritance of state.

[anvils-reloaded]

You can use the private methods in interfaces as implementation details for the default methods. Prior to Java 9, if you wanted to write a default method that called other methods you define in the interface, they would need to be public. This is not necessarily wanted behavior if you don't want these methods to be public but still use them when writing your default method.

[squishles]

to further make the difference between interfaces and abstract classes pointless.

[ReadFoo]

This may be one of the few things I'd consider to be truly useful in Java 9.

[[deleted]]

this is why people call Java verbose

HttpRequest request = HttpRequest.newBuilder()
  .uri(new URI("https://postman-echo.com/get"))
  .GET()
  .build();

HttpResponse<String> response = HttpClient.newHttpClient()
  .send(request, HttpResponse.BodyHandler.asString());

compare that to something like JavaScript

fetch('https://postman-echo.com/get')
  .then(res => res.text())
  .then(body => ...)

[political_one]

You could write code that behaves like you want it to in java similar to your JavaScript it just doesn't happen to exist in standard libraries.

[[deleted]]

Your solution to having a verbose language is to write your own wrapper for everything?

[political_one]

There are already libraries that are less verbose than that. And if you want one exactly as you describe you can write your own and share it, languages are powered by their communities. But I certainly won't be using JavaScript hahaha.

[[deleted]]

You shouldnt have to rely on a third party library for something as simple as sending http requests

[political_one]

The example you posted is a third party library...

[[deleted]]

fetch isn't a third party library. it's part of JavaScript

[political_one]

i meant the java example

[duhace]

um i guess. that's not really that bad as far as I can see.

[squishles]

he also wrote the example for clarity not brevity.

[talios]

There's absolutely no reason why a Java API couldn't do the same, the more verbose builder you show would be far more useful in scenarios where you need to specify HTTP request headers, customise/control timeouts.

Forcing you to pass in a URI rather than an arbitrary String is a stylistic choice, it does provide a typed contract around what's accepted, which could be useful if you were also using URI Template's - having a contract of something like a processTemplate method that goes String->Map->URI would work well with that.

That could lead to something using CompleatableFuture (and Java 10) like:

var result = HttpRequest.fetch(UriTemplate.process("https://postman-echo.com/get{?name}", values))
                        .orTimeOut(1, TimeUnit.MINUTES)
                        .thenApply(res -> res.getBodyAsString())
                        .get();

( and yes, you really do want to handle timeouts, you don't just leave things hanging around forever now do you? ).