Part 1 : Java Platform

Problems Questions
Problem 1 Why is Java so Popular?
Problem 2 What is Platform Independence?
Problem 3 What is ByteCode?
Problem 4 Compare JDK vs JVM VS JRE.
Problem 5 What is the role of class loader in java ?

Part 2 - Wrapper Classes

Problem Questions
Problem 1 What are wrapper classes?
Problem 2 Why do we need Wrapper Classes in Java?
Problem 3 What are the different ways of creating Wrapper Class Instances?
Problem 4 What are differences in the two ways of creating wrapper classes ?
Problem 4 What is Auto Boxing?
Problem 5 What are the advantages of Auto Boxing?
Problem 6 What is Casting?
Problem 7 What is Implicit Casting?
Problem 8 What is Explicit Casting?

Part 3 - Strings

Problem Questions
Problem 1 Are all String’s immutable?
Problem 2 Where are string values stored in memory?
Problem 3 Why should you be careful about String Concatenation(+) operator in Loops?
Problem 4 How do you solve above problem?
Problem 5 What are differences between String and StringBuffer?
Problem 6 What are differences between StringBuilder and StringBuffer?
Problem 7 Can you give examples of different utility methods in String class?

Part 4 - OOP’s

Problem Questions
Problem 1 What is a Class?
Problem 2 What is state of an Object?
Problem 3 What is behavior of an Object?
Problem 4 What is the super class of every class in Java?
Problem 5 Explain about toString method ?
Problem 6 What is the use of equals method in Java ?
Problem 7 What are the important things to consider when implementing equals method?
Problem 8 What is the hashCode method used for in Java?
Problem 9 Explain inheritance with Examples.
Problem 10 What is Method Overloading?
Problem 11 What is Method Overriding?
Problem 12 Can super class reference variable can hold an object of sub class?
Problem 13 Is Multiple Inheritance allowed in Java?
Problem 14 What is an Interface ?
Problem 15 How do you define an Interface ?
Problem 16 How do you implement an interface ?
Problem 17 Can you explain a few tricky things about interfaces ?
Problem 18 Can you extend an interface ?
Problem 19 Can a class implements multiple interfaces ?
Problem 20 What is an Abstract Class ?
When do you use an Abstract Class ?
How do you define an Abstract Method ?
Compare Abstract Class vs Interfaces ?
Problem 21 What is a Constructor?
Problem 22 What is a Default Constructor?
Problem 23 Will this code compile?
Problem 24 How do you call a Super Class Constructor from a Constructor?
Problem 25 Will this code Compile?
Problem 26 What is the use of this()?
Problem 27 Can a constructor be called directly from a method?
Problem 28 Is a super class constructor called even when there is no explicit call from a sub class constructor ?
Problem 29 Difference between compile time and run time polymorphism - Link