Experienced Java Interview questions asked by CGI

3+ Year experienced java questions asked by CGI.

       1)  Tell me about your self ?

    Ans : Just describe yourself with cool & confidence.

    
2) What you know about our company?

   Ans : Remember , it’s a very crucial question. You must do one R&D before going to interview. You should know about their product, technical stuffs they are working, market value of the company and other important stuffs.

3) What is transient variable ?

   Ans : Transient variables are not serializable. It helps to avoid a variable to being serialization.

4) Write the code to initialize the inner class members.

Ans : Code here

public class InnerClassTest {

      class innerTest{

            private int age;

           

            public void display(){

                  System.out.println("Age="+age);

            }

      }

      /**

       * @param args

       */

      public static void main(String[] args) {

            InnerClassTest.innerTest innerObj=new InnerClassTest().new innerTest();

            innerObj.age=20;

            innerObj.display();

      }

}

 5) How to retrieve the elements from the collection write the code ?

Ans : Java provides certain interfaces by using that we can retrieve the elements from collection.Example – Iterator, ListIterator and Enumeration.

Example :- ArrayList data retrival

public class ArrayListRetrive {

      /**

       * @param args

       */

      public static void main(String[] args) {

            ArrayList<String> arList=new ArrayList<String>();

            arList.add("Java");

            arList.add("is");

            arList.add("Powerful!!!");

           

            //Retrive elements from ArrayList using Iterator

            Iterator iTer=arList.iterator();

            while(iTer.hasNext()){

                  System.out.println(iTer.next());

            }

      }

}

6) What is static and instance variables and methods ?

Ans : Static variables are per class but the instance variables are per object. All object share a single copy of static variable. In case of static method , no need of object creation for calling static method. The static method can directly call by using class name. Instance method need object for calling.

7) What is dynamic loading and static loading of java class ?

Ans : Dynamic class loading is by Class.forName() , which loads the class dynamically. Also you can use reflection for dynamic class loading. But, the static class loading is working by using ‘new’ keyword.

8) What type of loading is class.forname() ?

Ans : Its dynamically locate and loads the class.

9) What is Hibernate 3 best benefits ?

Ans : There are many benefits of hibernate. But the most benefits are below :-

1.     It reduces the developer effort to writing queries.

2.     Its easy to use with relational object which maps with java class and database relation.

3.     Query tuning is not required and it implements separates cache which is reason for better performance.

10) I have 100 tables and fields. I want to find one table name and  column names.  Write a quey .

Ans :  I have used MySQL database for this below query.

select TABLE_SCHEMA,TABLE_NAME,COLUMN_NAME from information_schema.COLUMNS where TABLE_NAME='EMPLOYEE';

 11) How to define a field name in hibernate using annotation ?

          Ans:- @Column  (Its provided by java persistent  API).

 12) What is Synchronization ?

          Ans:- Synchronization is a solution for concurrency issue. Java provide 'synchronized' keyword for implementing this.

  13) The most commonly used classes in collections ?

Ans : ArrayList, LinkedList, HashTable, HashMap and ConcurrentHashMap, etc.