How to create singleton class? What is the use of Proguard and How Proguard internally works? Write code to implement ViewModel What is the difference between apk and aab?

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Accepted Answer

A singleton class is a class that can only have one instance created at a time. Proguard is a tool used for code obfuscation and optimization. ViewModel is a class that stores and manages UI-related data.

To create a singleton class, make the constructor private, create a static method to return the instance, and use a static variable to hold the instance.
Proguard is used to shrink, optimize, and obfuscate the code in an Android application to make it smaller and more efficient.
ViewModel is a part of the Android Architecture Components that is used to store and manage UI-related data in a lifecycle-aware way.
APK is the standard format for Android apps, while AAB (Android App Bundle) is a new publishing format that includes all the app's compiled code and resources, but defers APK generation and signing to Google Play.

How to create singleton class? What is the use of Proguard and How Proguard internally works? Write code to implement ViewModel What is the difference between apk and aab?

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