Interview QA

This page will contain the basic interview questions and answer for java people, for experienced and fresher both can read this  blog and will help in understanding the interviewers mind.

Basic Java Questions -

1. Why string is immutable in java ?

2. What is  Serializable and Externalizable in java ?
     How to customize serialization process ?

3. Can we serialize static variables of class ?

4. Static variables are associated with class or Object ?

5. At which level serialization happens object or class ?

6.  Can transient variable be serialized explain ?

7.  how to make any class immutable in java ?

8. Difference between String Builder and String Buffer ??

9. How to revers any string example String test=new String("I am ashish") output should be "ashish am i" ?

10. write down sql query for finding out name of employee and there manager .

Employee Table with 3 column 

E_Name E_Name Manager_ID

Where Manager_ID is the subset of E_ID

11. what is instance variable, static variable in java ?




Adding few more questions -


1. why hashtable allow null key and values not hashmap 

2. what is the significance of thread.start() and thread.run() method ..

3. How hashmap work while passing key and value as a class

Employee class and Salary class

Implement in such a way to get the salary corresponding to each employee.

4. equals and hashcode logic

5. Employee emp1=new Employee("ashish");
Employee emp2=new Employee("ashish");

emp1.equals(emp2) // what will be the output

6. If we have list of employees ..how we sort based on emp_name and emp_id?

7. 

Class A
{

method m1()
}

class B
{

}

main()
{

A a=new B()

a.m1 // what will happen here
}


Class A
{
}
Class B
{

method m1()
}

main()
{

A a=new B()
a.m1()// what will happen here

8.

String str1="ashish";
String str2=new String("ashish");

if(str1.equals(str2)) // output

if(str1==str2) // output

Explain the output ?

9. Design pattern singleton,adaptor,facade,decorator patter ?