Top 95 Core Java Interview Questions - Java Interview Questions

What is the difference between an Interface and an Abstract class ?
What is the purpose of garbage collection in Java, and when is it used ?
Describe synchronization in respect to multithreading ?
What are pass by reference and passby value ?
What is HashMap and Map ?
Difference between HashMap and HashTable ?
Difference between Vector and ArrayList ?
What is static keyword in java ?
What do you mean by platform independence ?
What is a JVM ?
What is the difference between a JDK and a JVM ?
What is Singleton class ?
What do you mean by Constructor ?
What is finalize() method ?
What is an Exception ?
What do you mean by Checked Exceptions ?
Explain Runtime Exceptions ?
When throws keyword is used ?
How finally used under Exception Handling ?
What is Polymorphism ?
What is Abstraction ?
What is Encapsulation ?
What is Abstract class ?
What is an Interface ?
Define immutable object ?
What is Comparable Interface ?
Explain the Java Program : public static void main (String args[ ]) ?
What is static block ?
What is function overloading ?
What is function overriding ?
Difference between Overloading and Overriding ?
What is final class ?
What is NullPointerException ?
What are the ways in which a thread can enter the waiting state ?
What invokes a thread's run() method ?
Does it matter in what order catch statements for FileNotFoundException and IOException are written ?
What is the difference between yielding and sleeping ?
What is the difference between the Reader/Writer class hierarchy and the InputStream/OutputStream class hierarchy ?
What is Serialization and deserialization ?
What's the difference between constructors and other methods ?
Is there any limitation of using Inheritance ?
What's the difference between the methods sleep() and wait()?
What is a transient variable ?
What is synchronization ?
Does garbage collection guarantee that a program will not run out of memory ?
What is the difference between a break statement and a continue statement ?
How can a dead thread be restarted ?
What will happen if static modifier is removed from the signature of the main method ?
What is the difference between error and an exception ?
Is it necessary that each try block must be followed by a catch block ?
What are synchronized methods and synchronized statements ?
Where and how can you use a private constructor ?
Describe life cycle of thread ?
Why Generics are used in Java ?
Why Strings are immutable ?
How to make a java class immutable ?
Deep copy and shallow copy ?
What is synchronization? Object level locking and class level locking ?
Can you assign null to this reference variable ?
How to override equals and hashCode() methods ?
Explain all access modifiers ?
What is native keyword? Explain in detail ?
What if the main method is declared as private ?
What if the static modifier is removed from the signature of the main method ?
What if I write static public void instead of public static void ?
What are different types of inner classes ?
How do I serialize an object to a file ?
Which methods of Serializable interface should I implement ?
When you serialize an object, what happens to the object references included in the object ?
What happens to the static fields of a class during serialization ?
How are Observer and Observable used ?
What is the difference between static and non-static variables ?
How does a try statement determine which catch clause should be used to handle an exception ?
What is difference between String, StringBuffer and StringBuilder? When to use them ?
Why String class is final or immutable ?
Is Java Pass by Reference or Pass by Value ?
What is the use of the finally block ? Is finally block in Java guaranteed to be called ? When finally block is NOT called ?