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06: HashMap & HashSet and how do they internally work? What is a hashing function?

HashMap & HashSet are not only one of the frequently used data structures, but also one of the popular interview topics. Q1. How does a HashMap store data? A1. As key/value pairs. You can store and retrieve values with the keys. … Read more ›...

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5 Java Object class methods interview questions & answers

Q1. What are the non-final methods in Java Object class, which are meant primarily for extension? A1. The non-final methods are equals( ), hashCode( ), toString( ), clone( ), and finalize( ). These methods are meant to be overridden. … Read more ›...

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8 Java immutable objects interview questions & answers

Best Practice: “Classes should be immutable unless there’s a very good reason to make them mutable….If a class cannot be made immutable, limit its mutability as much as possible.” — by Joshua Bloch Q1. What is an immutable object? Q2. Immutable objects are objects whose state (the object’s data) cannot...

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Java enum interview questions & answers

Covers the power of enumand 3 design patterns that can be applied with the help of enums. Q1. Why is it a best practice to use enums over static final int or String constants? A1. 1) static final allows invalid values. … Read more ›...

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Java serialization, cloning, and casting interview Q&A

Q1. Which Java interface must be implemented by a class whose instances are transported via a Web service? a. Accessible b. BeanInfo c. Remote d. Serializable A1. Answer is “d”. Q2. What is serialization? A2. … Read more ›...

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Mocks, stubs, domain, and anemic objects interview Q&A

Q1. What are mock objects? A1. Mock objects are used in unit testing to ensure that your tests don’t fail due to volatility of the data changes. There are mocking frameworks like EasyMock, Mockito, and PowerMock. … Read more ›...

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Object equals Vs == and pass by reference Vs value

Q1. What is the difference between “==” and equals(..) method when comparing 2 objects?
A1.It is important to understand the difference between identity (i.e. ==) comparison, which is a shallow comparison that compares only the object references, and the equals( ) comparison,

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