Practical tasks in Java, a good and understandable material on OOP?

Question

Java

Hello! I started my way in mastering programming languages, I started with Pascal and switched to learning Java, in fact, what I encountered: there is not enough practice, just some classes (like Alya make a primitive calculator through a switch case), to work out what has already been studied, there are some materials , sites, articles where to get Java tasks for beginners? I also got to OOP, the principle is clear, we don’t write huge code, we create another file, we write everything there, in the main file we refer to what is required. But it is not clear with the syntax in OOP which operators and classes. Thanks, I'll be glad to hear your answers!

Answer 1

https://www.hackerrank.com/domains/java
https://app.codility.com/programmers/
https://codingbat.com/java
Google - Java exercises or java oop exercises.
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