• Difference between array and ArrayList? • Difference between Set and List? • Set and List are classes or interfaces? • What is ArrayList’s parent class? • Is possible to use primitive types in arrays? • Is possible to use primitive types in List? • What is Generics? • Why is not possible to use primitive types in List? • What is Generics? • Why is not possible to use primitive types in Generics ? • Difference between StringBuilder and StringBuffer ? • How does Garbage Collector work? • What is the command to call GC execution? • Difference between memory heap and stack? • How do microsservices work? • How do we define security for application access?