Oracle Application Developer interview questions

Second round was set up on April-19-2021 This round was almost similar to first round, but the questions were little deep and twisted Had a competitive coding kinda question A recursion based question, here they interrupted and questioned to know my understanding on how recursion works SQL query question Few java oops concepts based questions

Third round happened on April-20-2021 In this round i had to explain about my current role and responsibilities. About the project that I am currently working. Then the questions turned out to be system design based questions. Questions were like, how will i scale the current system for more users, what could be the cons and bottle necks Difference between JRE and JVM How does the garbage collector work

Fourth round was on April-22-2021 The round started with me briefing on my current project and the work I do Few questions on why it was designed the way it is Then what design patterns that I know. I explained Singleton with a quick java code for the same. There were couple of questions like what would happen if the constructor is made public and the instance initialisation is done in the constructor rather than having a static getInstance() method Then explained Factory and builder patterns with java code What is cloning? What is serialisation? What is constructor chaining? What is reflection? What is the difference between hashmap and hashtable?