Java Interview Questions and Answers

What is the Vector class?
The Vector class provides the capability to implement a growable array of objects.
What is an Iterator interface?
The Iterator interface is used to step through the elements of a Collection .
Which java.util classes and interfaces support event handling?
The EventObject class and the EventListener interface support event processing.
What is the GregorianCalendar class?
The GregorianCalendar provides support for traditional Western calendars
What is the Locale class?
The Locale class is used to tailor program output to the conventions of a particular geographic, political, or cultural region .
What is the SimpleTimeZone class?
The SimpleTimeZone class provides support for a Gregorian calendar .
What is the Map interface?
The Map interface replaces the JDK 1.1 Dictionary class and is used associate keys with values.
What is the highest-level event class of the event-delegation model?
The java.util.EventObject class is the highest-level class in the event-delegation class hierarchy.
What is the Collection interface?
The Collection interface provides support for the implementation of a mathematical bag - an unordered collection of objects that may contain duplicates.
What is the Set interface?
The Set interface provides methods for accessing the elements of a finite mathematical set. Sets do not allow duplicate elements. .
What is the difference between the size and capacity of a Vector?
The size is the number of elements actually stored in the vector, while capacity is the maximum number of elements it can store at a given instance of time.
Can a vector contain heterogenous objects?
Yes a Vector can contain heterogenous objects. Because a Vector stores everything in terms of Object.
Can a ArrayList contain heterogenous objects?
Yes a ArrayList can contain heterogenous objects. Because a ArrayList stores everything in terms of Object.
What is an enumeration?
An enumeration is an interface containing methods for accessing the underlying data structure from which the enumeration is obtained. It is a construct which collection classes return when you request a collection of all the objects stored in the collection. It allows sequential access to all the elements stored in the collection. Considering the basic properties of Vector and ArrayList, where will you use Vector and where will you use ArrayList? The basic difference between a Vector and an ArrayList is that, vector is synchronized while ArrayList is not. Thus whenever there is a possibility of multiple threads accessing the same instance, one should use Vector. While if not multiple threads are going to access the same instance then use ArrayList. Non synchronized data structure will give better performance than the synchronized one.
Can a vector contain heterogenous objects?
Yes a Vector can contain heterogenous objects. Because a Vector stores everything in terms of Object.
Describe synchronization in respect to multi-threading?

With respect to multithreading, synchronization is the capability to control the access of multiple threads to shared resources. Without synchronization, it is possible for one thread to modify a shared variable while another thread is in the process of using or updating same shared variable. This usually leads to significant errors. 

Latest Updates

Simple Interest

The rate of simple interest on a sum of money is 6 percent per annum for first 3 years, 8 percent per annum for the next 5 years and 10 percent per annum for period beyond 8 years. If simple interest accrued by the sum for a total period of 10 years is Rs 1560, What is the sum?

Percentage

Shirin went to a bakery and bought items worth Rs 25, out of which 30 paise went on sales tax on taxable purchases. If the tax rate was 6%, then what was the cost of the tax free items?

Blood Relation

Pointing to a photograph, a man said, "I have no brother or sister but that man’s father is my father’s son." Whose photograph was it?

Introducing a man to her husband, a woman said "His brother's father is the only son of my grandfather". How is the woman related to the man ?

Apache Tomcat

What is the difference between Apache Tomcat server and Apache web server?

MS-DOS

What is the full form of DOS?

Explain the use of help DOS Command?

How we can create a directory in DOS?

Analogy

Riddle:Solve

Limp:Walk

Molecule:Atoms

Misfortune:Catastrophe

Pipes and Cistern

A tank can be filled by one tap in 10 minutes and by another in 30 minutes. Both the taps are kept open for 5 minutes and then the first one is shut off. In how many minutes more is the tank completely filled?

Simplification

Assume that a sum of money is divided equally among n girls. Each girl will receive $60. If another girl is added to the group and the sum is divided equally among all the girls, each child girl gets a $50 share. What is the sum of money?

Problems on Trains

A 300 meter long metro train crosses a platform in a metro station in 39 seconds while it crosses a lamp post in 18 seconds. What is the length of the platform?

Problems on Ages

In a group of 7 people, the average age is found to be 17 years. Two more people joined with an average age 19 years. One person left the group whose age was 25 years. What is the new average age of the group?

Profit and Loss

Irvin sold a book at a profit of 12%. If Irvin had sold it for Rs 18 more, then 18% would have been gained. Find the cost price?

Chemistry

Non stick cooking utensils are coated with?

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