Interview Summary:

My background (while attending the interview): 4+ years of experience as a Java Developer, with 2+ years of experience in another product development company.

Interview Details: Time: End of March 2018, for experienced Java Developers Total Rounds: 3 Venue: PayPal office, Chennai Result: Positive

All three rounds included common questions such as 'Tell me about yourself,' 'Describe your previous project,' and 'Why are you switching companies?'

1. Inheritance vs. Composition

• What is inheritance?
• What is composition?
• Use cases for each.
• Which is preferable?
• What are the drawbacks of inheritance?
• Are there any rules for choosing between them?
• Given an example, which one do you think is suitable for this example?

1. Collections Framework

• HashMap and ArrayList internal implementation.
• What is hashCode()?
• How is the get operation performed?
• equals() vs. hashCode()?

Class Employee { Name; Age; Salary; }

HshMap<Employee, BigInt> map;

• Can you add Employee to the map now?
• What are the prerequisites?
• What needs to be done?
• Write code for equals() overriding in this case.
• Use of hashCode()?

1. Generics – Java

• Why use generics?
• Purpose?
• Syntax?
• Benefits?

1. Thread Concepts

• Thread lifecycle.
• How are threads implemented?
• How do you run a thread?
• What is the synchronized keyword and when is it used?

1. Immutability

• What is immutability?
• Why do we need it?
• What does thread safety mean?

1. Design Patterns

• Talk about the Visitor pattern.
• When to use the Singleton pattern? Explain.

1. Data Structures

• Implement a Stack using any suitable data structure.