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Vibe Coding, Kotlin, Finance, and Data Visualization

Recently, I came across a paper discussing an experiment and tried to reproduce it. Here’s a brief summary: - Portfolio A: In a bull market, grows by 20%; in a bear market, drops by 20%. - Portfolio B: In a bull market, grows by 25%; in a bear market, drops by 35%. - Bull market probability: 75%. According to the paper, both portfolios should have a one-year expected return of 10%.

Treat life like a marathon, not like a sprint

Like most of us, I am daily flooded with thoughts about life, my objective position in it, whether I am missing anything, or whether I need to do better. Am I providing enough for my family? Is my career on track? Am I being healthy enough? Am I just passing through life instead of aiming to strive? Those thoughts have been slowly mitigated, but they never got away. Over time, I have been slowly accepting this reality, and I came to realise that all the marathon training and long-distance running have helped me come to terms with these facts.

Uploading SARIF Reports to GitHub

Recently I wanted to add Lint reports to a repository on GitHub. The goal is to report potential Lint violations when new code is committed, to make sure that all the committed code is lint-warning-free and pretty. My first idea was to look for a GitHub action that could run ./gradlew lint and report it as a PR comment. After asking about ideas in the Android Study Group, Carter Jernigan and Justin Brooks suggested me to upload directly the SARIF files into GitHub.

KotlinConf 2024 announcements

The first day of the KotlinConf 2024 is over, and there has been a significant amount. After 5 years the conference happened again at The Bella Center in Copenhagen, a fantastic venue close to the historical center of the Danish capital. The last two weeks have been intense, with the Google I/O announcing another set of relevant features for Android and Kotlin developers. Most notably, Google is now supporting KMP for Android development.

HTTP chunk requests with Android and ktor

In this very short article, I will explain briefly what is a chunk or streamed HTTP request, what are the benefits of using it, and how it works in Android. Android apps use HTTP requests to download data from a backend. This information is stored and processed on the app to make it functional. HTTP requests are executed using different frameworks on Android. The most common ones are Retrofit or OkHttp.

My Investing Summary of 2022

Another solar rotation passed, and the world experienced a plethora of unexpected events. In the aftermath of the Corona epidemic that altered the course of the last couple of years, we had the unfortunate invasion of Ukraine by Russian forces, the tightening of Corona measures in China (and toward the end of the year, their withdrawal and gradual reopening of the economy), an ongoing economic recession, the rate hike by the FED and the general uncertainty of the most immediate future.

KMP, iOS Developers and Production

Kotlin Multiplatform (or KMP, KMM Mobile, etc) has been widely used for a number of years in applications that are currently in production. JetBrains compiled a website listing some of the companies that are currently using KMP. Since the advent of the mobile platforms we enjoy today, there has always been a certain market interest to push multiplatform technologies, such as Cordova, Xamarin, and others. With more or less success, those technologies aimed to provide a unified framework to develop multiple codebases, mostly focusing on the aspect of pricing (create code once, deploy multiple times).

A recapitulation of investing in pandemic times

It has been around 14 months since the pandemic started. We have all been affected by it to a greater or lesser degree, and the investing world has not been an exception (although surprisingly, the stock market is one of the winners of the pandemic). In this post I will share how the pandemic changed my investment thesis, the things I learned, and the mistakes I did. 14 months into the crisis of our generation (and with a few months to recover whatever the new normal will be), we now know that things will never be the way they used to be.

A short story of randomness (I)

I have always been fascinated by the above comic strip. A discussion on randomness and determinism becomes as much a philosophical issue as it is a practical one. They are used in a variety of applications: from the obvious cryptography, gaming or gambling to the less evident politics or arts. How can we be sure that a number is random? Will observing the process mine our efforts on generating the random number, similar to the observation of a cat inside a box with a decaying radioactive atom?

From Java to Kotlin and back (III): Calling Java from Kotlin

This article is part of a series. You can find the remaining article of the series here: From Java to Kotlin and back (I) — Calling Kotlin from Java From Java to Kotlin and back (II): Calling Kotlin from Java In this last chapter of the series, we will evaluate consideration when calling Java code from Kotlin. One could argue that even in this situation happens often, keeping considerations in mind for some code that might legacy is not that practical.

From Java to Kotlin and back (III): Calling Java from Kotlin

Planted March 14, 2021

This article is part of a series. You can find the remaining article of the series here:

From Java to Kotlin and back (I) — Calling Kotlin from Java

From Java to Kotlin and back (II): Calling Kotlin from Java

In this last chapter of the series, we will evaluate consideration when calling Java code from Kotlin.

One could argue that even in this situation happens often, keeping considerations in mind for some code that might legacy is not that practical. Kotlin has also been designed with interoperability in mind, so Java code from Kotlin is much more “callable” than the other way around, since the design has been in mind since its conception. However, there are a few points that you can keep in mind when working on your Java code, and we would like to explain them in this article.

Annotations

Since Java lacks a few of the powerful features we already have on Kotlin, we will rely significantly on some annotations that can prepare our Java code to interface with Kotlin.

Nullability

Whereas nullability is one of the core features in Kotlin, Java does not provide out-of-the-box support for it. Every parameter in Java should always have a nullability annotation. Otherwise, they are understood as “platform types”, which have an ambiguous way to determine nullability and can trigger runtime errors, pretty much what Kotlin nullability aims to avoid. For example, consider the following piece of code:

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If we try to call the function doNotUseAnnotation with false, the code will trigger an Exception. Because we didn’t add any annotation, Kotlin implies that the function is not nullable. In Java, we would be setting up the nullability as follows:

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The most common ones that we will find are @Nullable and @NotNull, present in the package org.jetbrains.annotation but also in com.android.annotation and others, such as Lombok.

Generally, Java code that has not been properly annotated can lead to unpredictable behavior. If you have some experience in the Android realm, where the framework is written in Java, you will be constantly relying on annotations that are not all the time where they should be.

If you are working on Java code that will be potentially exposed to Kotlin, remember to use Nullability annotations to facilitate the lives on the other side of the fence.

@UnderMigration annotation

The @UnderMigration annotation is pretty useful when we are maintaining some Java code, and we want to inform our potential clients of its current status (please note that the annotation can be found in a separate artifact, kotlin-annotations-jvm)

@UnderMigration status can have three different values, similar to the explicit API mode introduced in Kotlin 1.4:

  • MigrationStatus.STRICT will deliver a compilation error when there is a misusage of an annotation, causing the code to fail.
  • MigrationStatus.WARN: similar to the previous one, but just dropping a warning
  • MigrationStatus.IGNORE ignores completely the usage of the annotations.

Getters and setters in Java

Kotlin uses property access instead of getters and setters, like Java. The definition of a getter is a no argument with a name starting with get, and the definition of a setter is a one-argument method with a name starting with set. Boolean getters start with is, so we can use a more natural human language to ask for the value of the property (isClosed, is Finished, etc). Keep this in mind when designing your Java class, although this is pretty much standard. Interestingly, if your attribute provides only a setter it will not be visible as a property, since Kotlin does not support set-only properties (and this is generally an anti-pattern).

The following Java class:

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will be accessed like the following block in Kotlin:

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Kotlin keywords

Kotlin has a few hard keywords that we should not be using in our Java code, since the Kotlin counterpart will need backticks to call them.

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Protip: these backticks can be used all around when naming methods and variables in Kotlin, not only in the case of hard keywords or tests.

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Summary

This last article presents tips to design and work on our Java code when it will be later on consumed in Kotlin. Java code can expose code to Kotlin with lesser effort than the other way around, but the points explored will be able to help you achieve a more efficient interoperable code.

I write my thoughts about Software Engineering and life in general on my Twitter account. If you have liked this article or it did help you, feel free to share, 👏 it and/or leave a comment. This is the currency that fuels amateur writers.