Java Interview Questions
- What is your understanding with serialization? Where you have use that?
- What is a difference between Abstract class and interface? Give example where you will you.
- Abstract class and where you will use interface.
- What is a difference between HashMap and Properties Class.
- Where instance variable are stored and where local variable are stored.
- Have you ever overridden equal method?
- What new features added to JDK 1.5? Explain few out of those?
- Which driver type you have use in JDBC connection and Why?
- What is the difference between Check and Uncheck exception? How exceptions are handled in your project.
- What is difference between Applet and servlet?
- What will be returned from this block.
- Difference between Set & Arraylist.
- Is Set a class or an interface?
- Can a private class be executed? How do we access public method of private class?
- If public static void main(String args) is changed to protected static void main(String args), will the class compile? Will the class be executed using java command?
- If public static void main(String args) is changed to public static void main(String name), will the class compile? Can the class be executed using java command?
- Is finally block manadatory in try/catch block?
- Can runtimeexception be extended?
- While overriding methods, what are rules applicable for Exception?
- While overriding methods, what are rules applicable for access modifiers?
- Can a class have a private constructors?
- What isi serialization?
- What is the difference between abstraction and encapsulation?
- What is the difference between abstract class and interface?
- What are the access specifiers and why interface has to be declared Public?
- What is the difference between Checked exceptions and unchecked exception?
- What are the rules for method overloading?
- What do you mean by threadsafe?
- Which collection is thread-safe? What will happen when 2 or more threads will try to insert data in an arraylist in a method which is not synchronized?
- When a method is thread safe, the thread will apply a lock on method level or Object level?
The example of try catch and finally block with return statement?
- Collections - Equals method vs Hashcode, use of Hashcode, best hashcode implementations, Vector vs Array list, Hashtable vs Hashmap, Generics.
- Threads - Join(), Wait() - study all the overloaded methods of wait, Notify() and NotyfyAll(), Sleep(),synchronization.
- String - String constant pool, Heap vs stack, Diff bet string vs string buffer
- General - Abstract class vs Interface( which one u will choose for which scenario), Access modifiers(Public,Protected,private and default), Overriding(Including static method override).
- Exception handling –
- Memory - Study about JVM and Garbage collections, Memory leak, Local vs class variable
core java design patterns(Singleton with thread safe, Factory pattern etc).
JSP/servlets – Session handling, security, JSP implicit objects, tags.
- What is diff between aggregation and composition? Give example
- What is encapsulation and abstraction?
- What is multiplicity?
- What is polymorphism and types of polymorphism?
- What is post difference between Post and Get request? When you use what?
- What is difference between <@ include> and <jsp:include>
- What is request forward and request redirect
- What is difference between stateful and stateless session beans?
- Why you have use EJBs?
- What is JNDI? Where you have used it? Can two connection pools have same JNDI?
- Give 5 ANT utilities you have worked on?
- What is M in Structs MVC? How it is implemented in struts?
- How action servlet works ?
- What is difference between SessionFactory and Session in Hibernate?
- What is lazy loading in hibernate? Which design pattern it follows?
- What is meaning of cascading=alldeleteorphan in hibernate mapping file?
- What is difference between L1 Cache and L2 Cache and how it is implemented in hibernate?
- How you have managed DB transaction in you project? How concurrency is controlled?
- ORM advantages & disadvantages.
- Configuring hibernate application(sessionfactory, entity generation, entity mapping, defining named queries)
- Criteria API.
- Cache mechanism(first level/second level)
- Transaction management.
- Overview of MVC
- Role of ActionServlet/Request Processor
- The J2EE design patterns implemented by action servlet/Request processor
- Request flow in struts
- Different action types.
- What is Singleton pattern? How you have implemented it? Why you use singleton pattern
- What is Factory Pattern and why it is used?
- What is your understanding with connection pooling
- Other queries based on resources skill set?
Problem Solving Approach:
- If there is a ticket raised by the client, the page that was opening in 5 seconds yesterday, is taking 4-5 mins today. What will be your approach to resolve this issue?
- Logic to remove duplicate character from a string and "how you will unit test your code"?
Sample questions asked by the client:
- Difference between checked vs. unchecked, and how to create unchecked exception.
- Hash code versus equal code.
- Queue/topic difference.
- What is transactionality when reading from JMS queues.
- How to write a template class.
- How to get ID’s out of a hibernate mappings.
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