Freemarker Template Language

1. Identifying whether an element is empty
2. Iterating over map using entryset

Web-Services

1. Testing web services using cURL

Spring sample implementations

1. RowMapper Example
2. BeanPropertyRowMapper Example

JVM, Memory management and Garbage Collection Concepts

1. How garbage collection works
2. Why full gc need stop the world
3. Garbage collection visualization (In visual vm)

Inter-thread communication using wait notify scenario

Question -  There are three threads,t1, t2 and t3, each of these thread have an array of size three. thread t1 has array {1,4,7}, thread t2 has array {2,5,8}, thread t3 has array {3,6,9}.

How to design the thread execution so that the output of execution will be 1,2,3,4,5,6,7,8,9 

Solution - It is an scenario of multi-thread communication being handled using wait & notify methods.
The code is as mentioned below - 

public class InterThreadCommunication {
    
    static class SampleRunnable implements Runnable
    {
        final int[] arrayToPrint;
        final Object waitMonitor;
        final Object notifyMonitor;
        
        public SampleRunnable(int[] arrayToPrint, Object waitMonitor, Object notifyMonitor) {
            this.waitMonitor = waitMonitor;
            this.notifyMonitor = notifyMonitor;
            this.arrayToPrint = arrayToPrint;
        }
        
        @Override
        public  void  run() {
            
            try {
                setCurrentMonitorToWait();
                
                System.out.println(arrayToPrint[0]);
                notifyNextMonitor();
                
                setCurrentMonitorToWait();
                
                System.out.println(arrayToPrint[1]);
                notifyNextMonitor();
                
                setCurrentMonitorToWait();
                
                System.out.println(arrayToPrint[2]);
                notifyNextMonitor();
                
                
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

        private void setCurrentMonitorToWait() throws InterruptedException {
            synchronized (waitMonitor) {
                this.waitMonitor.wait();    
            }
        }

        private void notifyNextMonitor() {
            synchronized (notifyMonitor) {
                this.notifyMonitor.notify();    
            }
        }
    }
    
    
    public static void main(String[] args) {
        
        Object firstMonitor = new Object();
        Object secondMonitor = new Object();
        Object thirdMonitor = new Object();
        
        int[] a1 = new int[] {1,4,7};
        int[] a2 = new int[]{2,5,8};
        int[] a3 = new int[]{3,6,9};
        
        Thread t1 = new Thread(new InterThreadCommunication.SampleRunnable(a1,firstMonitor,secondMonitor));
        Thread t2 = new Thread(new InterThreadCommunication.SampleRunnable(a2, secondMonitor, thirdMonitor));
        Thread t3 = new Thread(new InterThreadCommunication.SampleRunnable(a3, thirdMonitor, firstMonitor));
        
        t1.start();
        t2.start();
        t3.start();
        
        synchronized (firstMonitor) {
            firstMonitor.notify();
        }
    }

}

While testing in quad core processor machine, we found it working fine. But this solution might get into dead lock situation if first signal from main to first thread gets missed.

We could mitigate this problem, by using semaphore. The solution code is as mentioned below -

import java.util.concurrent.Semaphore;

public class InterThreadCommunication {
    
    static class SampleRunnable implements Runnable
    {
        final int[] arrayToPrint;
        final Semaphore acquireSemaphore;
        final Semaphore releaseSemaphore;
        
        public SampleRunnable(int[] arrayToPrint, Semaphore acquireSemaphore, Semaphore releaseSemaphore) {
            this.acquireSemaphore = acquireSemaphore;
            this.releaseSemaphore = releaseSemaphore;
            this.arrayToPrint = arrayToPrint;
        }
        
        @Override
        public  void  run()
        {
      try {
    
              this.acquireSemaphore.acquire();
              System.out.println(arrayToPrint[0]);
     
              this.releaseSemaphore.release();
              this.acquireSemaphore.acquire();
              System.out.println(arrayToPrint[1]);
              
              this.releaseSemaphore.release();
              this.acquireSemaphore.acquire();
              System.out.println(arrayToPrint[2]);
              this.releaseSemaphore.release();
                 
   } catch (InterruptedException e) {
    e.printStackTrace();
   }
        }
    }
    
    
    public static void main(String[] args) {
        
        Semaphore firstSemaphore = new Semaphore(0);
        Semaphore secondSemaphore = new Semaphore(0);
        Semaphore thirdSemaphore = new Semaphore(0);
        
        int[] a1 = new int[] {1,4,7};
        int[] a2 = new int[]{2,5,8};
        int[] a3 = new int[]{3,6,9};
        
        Thread t1 = new Thread(new InterThreadCommunication.SampleRunnable(a1,firstSemaphore,secondSemaphore));
        Thread t2 = new Thread(new InterThreadCommunication.SampleRunnable(a2, secondSemaphore, thirdSemaphore));
        Thread t3 = new Thread(new InterThreadCommunication.SampleRunnable(a3, thirdSemaphore, firstSemaphore));
        
        t1.start();
        t2.start();
        t3.start();
        
        firstSemaphore.release();
    }

}

As in this problem, at a moment of time, only one thread should be in action to give the result in a specific sequence. We can implement the solution using Exchanger as well. The implementation is as mentioned below -

import java.util.concurrent.Exchanger;

public class PipeLineOperation extends Thread {
    
  private int threadNumber;
  private Exchanger firstExchanger;
  private Exchanger secondExchanger;
  private int[] firstArray;
  private int[] secondArray;
  private int[] currentArray;
  
  public PipeLineOperation(int threadNumber, Exchanger firstExchanger, Exchanger secondExchanger, int[] threadsArray) {
   this.firstExchanger = firstExchanger;
   this.secondExchanger= secondExchanger;
   this.threadNumber = threadNumber;
   this.currentArray = threadsArray;
  }
 
  @Override
  public  void  run()
  {
   try
    {
      performOperationInthread();
    }
    catch(InterruptedException interruptedException)
    {
     throw new RuntimeException(interruptedException);
    }
  }

  private void performOperationInthread() throws InterruptedException {
   if(threadNumber == 0)
   {
     firstArray = currentArray;
     secondArray = firstExchanger.exchange(currentArray);
     currentArray = secondExchanger.exchange(currentArray);
          
          for (int i = 0; i < 3; i++) {
     System.out.println(firstArray[i]);
     System.out.println(secondArray[i]);
     System.out.println(currentArray[i]);
    }
   }
   else
   {
     currentArray = firstExchanger.exchange(currentArray);
   }
  }
    
    public static void main(String[] args) {
     Exchanger firstExchanger= new Exchanger<>();
     Exchanger secondExchanger = new Exchanger<>();

     new PipeLineOperation(0, firstExchanger, secondExchanger, new int[] {1,4,7}).start();
     new PipeLineOperation(1, firstExchanger, null, new int[]{2,5,8}).start();
     new PipeLineOperation(2, secondExchanger, null, new int[]{3,6,9}).start();
    }

}

The problem can be solved easily without using any synchronized construct, and implementing threads using callable construct. The complete working code is as following -

import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.FutureTask;

public class PipeLineOperation implements Callable {
    
 private final int[] holdingArray;
 
 public PipeLineOperation(final int[] holdingArray) {
  this.holdingArray=holdingArray;
 }
 
 @Override
 public int[] call() throws Exception {
  return holdingArray;
 }
    
    public static void main(String[] args) throws InterruptedException, ExecutionException {
     final ExecutorService executorService = Executors.newFixedThreadPool(3);
    
     final FutureTask firstFutureTask = (FutureTask) executorService.submit(new PipeLineOperation(new int[]{1,4,7}));
     final FutureTask secondFutureTask = (FutureTask) executorService.submit(new PipeLineOperation(new int[]{2,5,8}));
     final FutureTask thirdFutureTask = (FutureTask) executorService.submit(new PipeLineOperation(new int[]{3,6,9}));
     
     executorService.shutdown();
     
     final int[] firstArray = firstFutureTask.get();
     final int[] secondArray = secondFutureTask.get();
     final int[] thirdArray = thirdFutureTask.get();
     
     for (int i = 0; i < 3; i++) {
   System.out.println(firstArray[i]);
   System.out.println(secondArray[i]);
   System.out.println(thirdArray[i]);
  }
    }
}

The same problem can be solved using wait notify mechanism by designing SequenceLatch. The solution is as mentioned following -

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class SequencialLatchDemo {

 public static void main(String[] args) throws InterruptedException {

  SequencialLatch firstLatch = new SequencialLatch();
  SequencialLatch secondLatch = new SequencialLatch();
  SequencialLatch thirdLatch = new SequencialLatch();

  firstLatch.setNext(secondLatch);
  secondLatch.setNext(thirdLatch);
  thirdLatch.setNext(firstLatch);

  Runner runner1 = new Runner(new int[] { 1, 4, 7 }, 1, firstLatch);
  Runner runner2 = new Runner(new int[] { 2, 5, 8 }, 2, secondLatch);
  Runner runner3 = new Runner(new int[] { 3, 6, 9 }, 3, thirdLatch);

  ExecutorService service = Executors.newFixedThreadPool(3);
  service.submit(runner2);
  service.submit(runner3);
  service.submit(runner1);

  service.shutdown();
 }

}

class Runner implements Runnable {

 private final SequencialLatch pass;
 private final int[] numbers;
 private final int threadNumber;

 public Runner(int[] numbers, final int threadNumber, SequencialLatch pass) {
  this.numbers = numbers;
  this.pass = pass;
  this.threadNumber = threadNumber;
 }

 @Override
 public void run() {

  for (int taskNumber = 0; taskNumber < numbers.length; taskNumber++) {
   if (!(this.threadNumber == 1 && taskNumber == 0))
    pass.await();
   System.out.println(numbers[taskNumber]);
   pass.nextPerssionRelease();
  }
 }

}

class SequencialLatch {

 private SequencialLatch next;
 private boolean active;

 public void nextPerssionRelease() {
  this.active = false;
  next.active = true;
  synchronized (next) {
   next.notify();
  }
 }

 public void await() {
  while (!active) {
   synchronized (this) {
    try {
     this.wait();
    } catch (InterruptedException e) {
     e.printStackTrace();
    }
   }
  }
 }

 public void setNext(SequencialLatch existingPass) {
  this.next = existingPass;
 }
}

The same problem can be solved using Lock and Condistion mechanism by designing SequenceLatch. The solution is as mentioned following -

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

public class SequencialLatchDemo {

 public static void main(String... args) throws InterruptedException {

  SequencialLatch firstLatch = new SequencialLatch();
  SequencialLatch secondLatch = new SequencialLatch();
  SequencialLatch thirdLatch = new SequencialLatch();

  firstLatch.setNext(secondLatch);
  secondLatch.setNext(thirdLatch);
  thirdLatch.setNext(firstLatch);

  Runner runner1 = new Runner(new int[] { 1, 4, 7 }, 1, firstLatch);
  Runner runner2 = new Runner(new int[] { 2, 5, 8 }, 2, secondLatch);
  Runner runner3 = new Runner(new int[] { 3, 6, 9 }, 3, thirdLatch);

  ExecutorService service = Executors.newFixedThreadPool(3);
  service.submit(runner2);
  service.submit(runner3);
  service.submit(runner1);

  service.shutdown();
 }

}

class Runner implements Runnable {

 private final SequencialLatch pass;
 private final int[] numbers;
 private final int threadNumber;

 public Runner(int[] numbers, final int threadNumber, SequencialLatch pass) {
  this.numbers = numbers;
  this.pass = pass;
  this.threadNumber = threadNumber;
 }

 @Override
 public void run() {

  for (int taskNumber = 0; taskNumber < numbers.length; taskNumber++) {
   if (!(this.threadNumber == 1 && taskNumber == 0))
    pass.await();
   System.out.println(numbers[taskNumber]);
   pass.nextPerssionRelease();
  }
 }

}

class SequencialLatch {

 private final static Lock baseLock = new ReentrantLock();
 private final Condition condition = baseLock.newCondition();
 private boolean active;
 private SequencialLatch next;

 public void nextPerssionRelease() {
  baseLock.lock();
  try {
   this.active = false;
   next.active = true;
   next.condition.signal();
  } finally {
   baseLock.unlock();
  }
 }

 public void await() {
  baseLock.lock();
  try {
   while (!active) {
    condition.await();
   }
  } catch (InterruptedException interruptedException) {
   interruptedException.printStackTrace();
  } finally {
   baseLock.unlock();
  }
 }

 public void setNext(SequencialLatch existingPass) {
  this.next = existingPass;
 }
}

Max number existing in any of the participating table columns

Question - There are two tables (Ex - test1 & test2 ) having only one column of number type (Ex. number1 & number2). Write a query to find out max number existing in any of these tables.

Sample data setup query - 

CREATE TABLE test1( number1 NUMBER);
insert into test1 values (21);
INSERT INTO test1 VALUES (22);
INSERT INTO test1 VALUES (23);
INSERT INTO test1 VALUES (24);
insert into test1 values (25);


CREATE TABLE test2( number2 NUMBER);
INSERT INTO test2 VALUES (211);
INSERT INTO test2 VALUES (221);
INSERT INTO test2 VALUES (231);
INSERT INTO test2 VALUES (241);
insert into test2 values (251);

Three possible solutions - 

SELECT greatest((SELECT MAX(number1) FROM test1), (SELECT MAX(number2) FROM test2)) MAX FROM dual;

SELECT CASE WHEN (MAX(number1)>MAX(number2))
            THEN MAX(number1)
            ELSE
            MAX(number2)
            END CASE
from test1,test2;

SELECT MAX(number3) FROM 
(
  (SELECT MAX(number1)number3 FROM test1)
  UNION
  (SELECT MAX(number2)number3 FROM test2)
);

Selenium

Inportant information -

1. Selenium Documentation
2. Setting up selenium in eclipse

Multithreading Concepts

1. Thread-local, when & how to use it 
2. Thread local API
3. Interrupting other threads
4. Reasons to use multithreading
5. Concurrency tutorial
6. CyclicBarrier way of working
7. Creating thread pool using java executor framework
8. Thread pool executor - http://tutorials.jenkov.com/java-util-concurrent/executorservice.html
9. Starvation and livelock
10. Fork and join working and improvement from previous way
11. How to use ConcurrentHashMap
12. Java memory model in multithreading
13. Memory barriers and JVM concurrency

Xpath

1. Xpath Operators
2. Xpath functions

Webworks

1. Retriving application, session, request and page scopes

Finance and investing

1. Insurance planning
2. Ways to waste money
3. Home loan payment tax benefit rules
4. Joint tax filing in India is not applicable
5. Tax saving via family route

Security Interview Questions

1. Top ten web attacks - 
2. Cross site attack 
3. Preventing cross site attack  
4. Network layer
5. What is SSL Certificate
6. SSL Frequently asked questions
7. Tomcat SSL configuration
8. SSL Handshake
9. Securing web application using SSL
10. Java application using SSL
11. Key Tool, Creating Self Signed Certificate
12. Understanding SSL handshake

Servlet interview questions

Fundamental Based -

1. Java revisited servlet interview questions & answers

Design related interview questions

1. Object oriented design principles
2. Software design interview questions
3. When to use interface
4. Java enum is class or interface
5. Java67 design pattern questions and answers
6. Java revisited programming interview questions
7. How to analyze the thread dump
8. Understanding various design patterns
9. UML class diagram understanding & creation
10. Points to consider while implementing Observer design pattern
11. Difference between dependency injection and dependency lookup
12. How to program multithreading communication 
13. Managing code maintainability 
14. Maintaining code robustness 
15. Implementing extensible code
16. Optimistic concurrency control concept
17. Optimistic vs Pessimistic locking in Hibernate
18. What is time complexity
19. What is big O notation 
20. How to calculate the complexity of algorithm  
21. Sorting Algorithms -
    
    • Merge Sort 
    • Insertion Sort
22. Searching Algorithms -
    
    • Hash Table  
    • Binary Search Tree
    • B Tree 
    • B+ Tree

Spring-Core interview questions

Implementation Based - 

Auto wiring -

http://www.coderanch.com/t/603029/Spring/Autowired-properies

Common Questions - http://javarevisited.blogspot.in/2011/09/spring-interview-questions-answers-j2ee.html

Fundamental - 

http://java67.blogspot.sg/2012/08/spring-interview-questions-answers.html 

1. Can we assign the reference of prototype bean to singleton bean & vise versa ?
2. Is spring singleton , singleton to class-loader or not ?
3. Difference in life cycle of singleton and prototype bean ? (hint - destroy-method execution)

Link - http://static.springsource.org/spring/docs/3.2.x/spring-framework-reference/html/beans.html#beans-factory-scopes

1. Spring annotations and their purpose
2. Difference between <context:annotation-config> and <context:component-scan>
3. Register singleton bean to spring factory using registerSingleton

Jsp interview questions

1. EL String comparision
2. EL String to number comparision
3. Revisited JSP interview question
4. Simple tag life cycle (Simple tag support)
5. Body tag life cycle (Body tag support)

Core java fundamental interview questions

1. In the non-static method, the reference to the instance of the enclosing context is passed implicitly in the constructor call of the non-static local class
2.  Equals , comparable and comparator - http://leepoint.net/notes-java/data/expressions/22compareobjects.html
3. Common Question - http://bateru.com/news/2011/03/484/
4.  Common question - http://www.fromdev.com/2010/08/10-jdbc-questions-for-java-beginners.html
5. Good questions - http://javarevisited.blogspot.in/2011/04/top-20-core-java-interview-questions.html
6. Multithreading  - http://www.fromdev.com/2008/05/java-threading-questions.html
7. Collection - http://www.fromdev.com/2008/05/java-collections-questions.html
8. Classpath - http://www.fromdev.com/2012/09/Java-Path-Classpath-Questions-Answers.html
9. Jdbc - http://www.fromdev.com/2010/08/10-jdbc-questions-for-java-beginners.html
10.  Why static method override is not allowed
11. Starting thread more than once - http://stackoverflow.com/questions/1215548/is-it-legal-to-call-the-start-method-twice-on-the-same-thread
12. Wait notify- notify all - http://javarevisited.blogspot.sg/2011/05/wait-notify-and-notifyall-in-java.html 
13. Volatile vs synchronization - http://javarevisited.blogspot.in/2011/06/volatile-keyword-java-example-tutorial.html
14. HashTable vs Concurrent HashMap vs SyncronizedMap - http://javarevisited.blogspot.sg/2011/04/difference-between-concurrenthashmap.html
15. HashSet Vs TreeSet -http://java67.blogspot.sg/2012/08/difference-between-hashset-and-treeset-java.html
16.  http://javarevisited.blogspot.sg/2011/08/what-is-polymorphism-in-java-example.html
17. http://java67.blogspot.sg/2012/08/difference-between-string-and-stringbuffer-in-java.html
18. http://javarevisited.blogspot.sg/2012/01/how-to-reverse-string-in-java-using.html
19. http://java67.blogspot.sg/2012/09/java-collection-interview-questions.html
20. http://java67.blogspot.sg/2012/09/what-is-new-in-java-7-top-5-jdk-7.html
21. http://java67.blogspot.sg/2012/08/10-java-coding-interview-questions-and.html
22. http://java67.blogspot.sg/2012/08/5-thread-interview-questions-answers-in.html
23. http://java67.blogspot.sg/2012/09/top-10-tough-core-java-interview-questions-answers.html
24. http://javarevisited.blogspot.in/2011/11/collection-interview-questions-answers.html
25. http://javarevisited.blogspot.in/2011/02/how-hashmap-works-in-java.html
26. http://javarevisited.blogspot.in/2011/04/top-20-core-java-interview-questions.html
27. http://javarevisited.blogspot.in/2012/12/difference-between-equals-method-and-equality-operator-java.html
28. http://javarevisited.blogspot.sg/2011/04/difference-between-concurrenthashmap.html
29. http://java67.blogspot.in/2012/09/java-collection-interview-questions.html

Other important questions - 

1. What are advantages and disadvantages of singleton
2. Fail safe and fail fast iterator & internal working on fail fast iterator
3. The way to synchronize hash map-
• By passing it to the constructor of HashMap
• By passing it to the constructor of HashTable
• By calling synchronizedMap method of collections class
• By providing custom synchronized implementation
4. ClassNotFoundException Vs NoClassDefFoundError
5. What is stackOverFlow Error and can it be caught 
6. New features in Java7
7. Caching on wrapper classes

Serialization interview questions - 

http://stackoverflow.com/questions/447898/what-is-object-serialization
http://javarevisited.blogspot.sg/2011/04/top-10-java-serialization-interview.html

http://www.fromdev.com/2012/06/15-java-serialization-interview.html

http://java-questions.com/Serialization-interview-questions.html

OCPJP topics

TDD implementation based interview questions

code structure while using mock - 
http://www.coderanch.com/t/603031/Testing/mock-return-method


Other important concepts -

1. Implementing Login Service in TDD way
2. TDD vs Test after approach
3. Easy mock vs Mockito
4. Comparing two file using Junit
5. TDD with spring transactional DAO layer

6. AbstractTransactionalJUnit4SpringContextTests API

Hibernate fundamental interview questions

Query cache vs second level cache -
http://www.coderanch.com/t/602070/ORM/databases/Query-Level-Cache
http://www.javalobby.org/java/forums/t48846.html
http://www.coderanch.com/t/526101/ORM/databases/Relation-Hibernate-Query-Cache-Level

Foreign key relationship managing (inverse)-
http://www.coderanch.com/t/479189/ORM/databases/inverse-hibernate
http://www.coderanch.com/t/218391/ORM/databases/Inverse

Other useful information -

1. What is inverse
2. Cascade in Hibernate
3. Hibernate fetching strategy change at run-time 
4. Hibernate query generation mechanism selection
5. Hibernate inheritance mapping strategy concept
6. Hibernate inheritance mapping strategy code
7. Hibernate implicit inheritance mapping
8. Hibernate collection and it's usage
9. Hibernate session flushing
10. Hibernate flushing strategy
11. Hibernate commit vs flush
12. Drawbacks of second level cache
13. Hibernate filters and their usage
14. Issues with primitive type mapping in Hibernate
15. Fetching strategy and their impact in sql query generation
16. Mapping  java enum to database column

Database interview questions

1. Trigger types
2. Transaction handling in oracle pl/sql
3. Clustered and Non-Clustered index 
4. SQL Query related interview question
5. Oracle general interview question - 1
6. Oracle general interview question - 2
7. Max number existing in any of the tables
8. Identifying left outer and right outer join
9. Difference between DBA and SYSDBA
10. What is table partitioning and when it should be done
11. Queries for table partitioning
12. Partitioning existing table using exchange partition
13. Partitioning existing table using dbms_redifinition
14. Getting table partition related information using all_tab_partition
15. SQL interview question series

     Analytic Interview Questions -

1. Handling table's heirarchical data in query
2. Analytical function query 
3. Analytical function based query
 

 

Core Java implementation based questions

Race Condition scenarios-

1. i++ not being an atomic operation
2. Join causes only the calling thread to wait for operation completion not to another thread calling join method on the same parent thread

Other good questions & Scenarios -

1. Develop a horse racing program
2. Scenario of identifying right monitor in thread and importance of Yield method
3. Controlling the sequence of execution in multithread scenario using wait-notify
4. Javarevisited multithreading interview questions
5. Dead lock Scenario in Money transfer module
• Buggy Code Scenario
• Solution to prevent dead lock Scenarios

Spring-orm implementation based question

Designing -
http://www.coderanch.com/t/602653/ORM/databases/dynamicall-decide-database-referred

Q- How to perform operations in transaction while using HibernateTemplate or JDBCTemplate?
Ans- a) transaction across multiple JDBCTemplate or HibernateTemplate
b) Declarative (aop or annotation base) & programmatic transaction management configuration

Q- Possible isolation levels  & propagation of a transaction and way to use it in Spring - 
http://en.wikipedia.org/wiki/Isolation_%28database_systems%29
http://static.springsource.org/spring/docs/3.0.x/spring-framework-reference/html/transaction.html#transaction-declarative-annotations
 http://static.springsource.org/spring/docs/1.2.9/api/org/springframework/transaction/annotation/Isolation.html 

Ques-Spring's @Transactional on class level applies to what methods?

Ans-http://stackoverflow.com/questions/28170851/springs-transactional-on-class-level-applies-to-what-methods#

Hibernate implementation based interview questions

1. Cascade and lack on inverse causing duplicate in many to many 
2. Implicit inverse in one to many relationship 
3. Implementing optimistic locking in Hibernate
4. Optimistic and pessimistic locking implementation in Hibernate
5. Using c3p0 connection pool in Hibernate
6. Using projection and distinct in detached Criteria query