👉 1 >> Java String

concat() Vs the + Operator for Concatenation

1. Identify the problems

👉 Step 1: I am using React Native version 0.63.2 like below, and I want to build an android app by using Fastlane for CI/CD integration.

As an Android developer, we have all worked with traditional layouts: LinearLayout and RelativeLayout. For me, I think it is quite an approach with everyone, but it will bring a lot of bad problems about performance in our application. Furthermore, with many complex layouts nowadays, using the old layouts to handle them is so difficult. Therefore, Google introduced the library in the 2016 Google I.O conference talk about ConstraintLayout — It helps to avoid problems that the old brings.

I am delighted to be here today to help you understand all of the things the new layout — ConstraintLayout. Even…


Java HashMap class is an implementation of Map interface based on hash table. It stores elements in key & value pairs which is denoted as HashMap<Key, Value> or HashMap<K, V>.

It extends AbstractMap class, and implements Map interface and can be accessed by importing java.util package. Declaration of this class is given below.

1. What is Java Home

Many Java applications need to know the location of a $JAVA_HOME directory. The $JAVA_HOME on Mac OS X should be found using the /usr/libexec/java_home command-line tool on Mac OS X 10.5 or later. On older Mac OS X versions where the tool does not exist, use the fixed path "/Library/Java/Home". The /usr/libexec/java_home tool dynamically finds the top Java version specified in Java Preferences for the current user. This path allows access to the bin subdirectory where command-line tools such as java, javac, etc. exist as on other platforms. …

The Android App Bundle is Android’s new, official publishing format that offers a more efficient way to build and release your app. The Android App Bundle lets you more easily deliver a great experience in a smaller app size, which can improve install success and reduce uninstalls. It’s easy to switch. You don’t need to refactor your code to start benefiting from a smaller app. And once you’ve switched, you’ll benefit from modular app development and customizable feature delivery.

Available in Android Studio 3.2 or later, Unity 2018.3 & 2017.4.17, and Cocos Creator 2.0.9 or later.

Use comments to include nonexecutable text in your code, as a note or reminder to yourself. Comments are ignored by the Swift compiler when your code is compiled.

If you are an Objective-C developer, and you are not familiar with modern languages like Python or Ruby, the code in the previous screenshots probably looked pretty strange. The Swift language syntax is a huge departure from Objective-C, which was based largely on Smalltalk and C.

The Swift language uses very modern concepts and syntax to create very concise and readable code. There was also a heavy emphasize on eliminating common programming…


Swift is a fantastic way to write software, whether it’s for phones, desktops, servers, or anything else that runs code. It’s a safe, fast, and interactive programming language that combines the best in modern language thinking with wisdom from the wider Apple engineering culture and the diverse contributions from its open-source community. The compiler is optimized for performance and the language is optimized for development, without compromising on either.

Swift is friendly to new programmers. It’s an industrial-quality programming language that’s as expressive and enjoyable as a scripting language. …

It’s best practice to have separate environments for your iOS apps, especially if they are communicating with any servers. For instance, consider an iOS app and three different available web backend environments: development, staging, and production.

What’s the best way to switch in the iOS app to use these different servers? What about all the other potential key/value pairs of information, like API keys — and what if some of that information needs to be secure and not checked into version control?

The simplest way is to create a file to store these environment variables as a string or other…



Xcode combined with the Swift programming language makes developing apps easy and fun.

Download Xcode from Apple Store


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