Interview Questions and Answers for 'T' | Search Interview Question

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Q1601. What happens to private variables during inheritance ?

Core Java

Ans. Private variables are not inherited. They are simply ignored and not made part of the derived object body.

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Q1602. Can we declare a class private ?

Core Java

Ans. We can declare an inner class as private and hence would be restricting it's access from outside. We cannot make outer class as private.

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Q1603. Why can't we declare on outer class as private ?

Core Java

Ans. Making an outer class as private will make it inaccessible from anywhere and would make it useless.

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Q1604. How can we hide a class in Java ?

Core Java

Ans. By encapsulating it within another class and declaring it private. In such a case, it will only be accessible through parent class or parent class object.

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Q1605. What is the use of final keyword ?

Core Java

Ans. final keyword is a modifier that means differently when applied to variables, methods and classes.

1. Final variable cannot be changed once initialized
2. Final method cannot be overridden
3. Final class cannot be sub classed

Sample Code for final variable

Sample Code for final method

Sample Code for final class

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Q1606. How would you explain the statement "Java Programs are collection of objects" ?

Core Java

Ans. Java Programs are collection of objects that communicates with each other to get a task accomplished. To add to those objects, there are common spaces ( static i.e common for objects belonging to a class ) that are used too.

We can visualize objects as departments of an organization in real world. Just like Task gets initiated in one department and then files are moved across different departments to get work done. In a similar fashion, a task is initiated in one object ( having main method ) and then information ( through POJOs / DTOs ) is moved across objects to accomplish a task.

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Q1607. Why iterators of an array list are fail fast ?

Core Java

Ans. Because it's access isn't synchronized and hence access / modification by multiple threads may lead to inconsistent state.

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Q1608. What problem we could have with ArrayList which aren't possible with Vectors ?

Core Java

Ans. ArrayLists aren't synchronized and hence doesn't allow synchronized access. As multiple threads can access an arraylist in parallel, it may result in an inconsistent state.

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Q1609. What is the quickest way to find count of duplicate elements in an arraylist, without using iteration or loops ?

Core Java

Ans. We can copy the elements to a Set and then find the difference of count between ArrayList and Set. As Set don't allow duplicates , they will be removed in the set.

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Q1610. Write a method, that compare two numbers and return the bigger one ?

Core Java

Ans. int compare(int a, int b) {
a>b? return a: return b;
}

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Q1611. Write a Program for insertion sort.

Core Java

^{This question was recently asked at 'Ola Cabs'.This question is still unanswered. Can you please provide an answer.}

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Very frequently asked. Usually among very first few questions.

Q1612. Define encapsulation in Java ?

Core Java

Ans. Encapsulation is a feature of OOP's that binds the data and it's associated methods together as a single unit and facilitate protection and data hiding by providing minimal interface to outside. For example - member variables are declared private and are accessed through public methods. Moreover we have private methods that can only be used internally and hence providing minimal interface to outside class through use of public methods.

Sample Code for encapsulation

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Q1613. Design a Coffee machine using Oops concepts.

Design

^{This question was recently asked at 'ECI Telecom'.This question is still unanswered. Can you please provide an answer.}

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Q1614. What is a shard in Kinesis stream ?

Amazon Web Services (AWS)

Ans. A shard is a uniquely identified group of data records in a stream or we can say that Shard is a partition in Kinesis stream. A shard supports a fixed bandwidth i.e fixed number of messages per second. The total capacity of the stream is the sum of the capacities of its shards. If the data rate changes, we can allocate / deallocate more shards to accommodate that.

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Q1615. What is the relationship between shard and partition key in kinesis stream ?

Amazon Web Services (AWS)

Ans. A partition key is used to group data by shard within a stream. A partition key identifies which shard the message belong to.

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Q1616. Solve the producer and consumer problem

Operating System

^{This question was recently asked at 'Dell'.This question is still unanswered. Can you please provide an answer.}

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Q1617. What do you understand by "Scaling Trigger" ?

Server

Ans. It's a configuration for auto scaling environment that specify the attributes / conditions for scaling instances up and down. For example - We may like environment to scale up when the number of requests / sec increases a particular threshold and scale down when it decreases below a threshold.

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Q1618. How can we know how many instances are currently in service within an Elastic Beanstalk environment ?

Amazon Web Services (AWS)

Ans. We can go to respective environment and check configuration and then scaling. It mentions that as current status like

Current status:

2 instance(s) in service, Min: 1, Max: 4

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Q1619. How can we get count of all keys within Redis ?

Redis

Ans. We can either do DBSIZE or KEYS *

Keys * will return the list of all keys too so DBSIZE is preferred if we just want the count.

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Q1620. What is the difference between "Manual Scaling" and "Auto Scaling" ?

Server

Ans. Manual scaling is the process of scaling instances up and down in a an enviornment manually by observing the scaling trigger whereas Auto scaling is the process wherein a Trigger condition specified as a scaling trigger will trigger scaling up and down of instances.

for example - If an organization has a policy of scaling up if requests / sec / instance exceeds 10000, Operations team will have to manually monitor the metric and they can request scaling up and down as the need arise. Manual scaling offers flexibility as team can scale on the basis of combination of factors and can take decision on flyby requires continuous monitoring.

The same trigger can be fed as triggering policy to the environment and can be taken care by the system. This requires availability of such triggering policy within the environment configuration but as it's automatically handled, requires no supervision.

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Q1621. How can we set a key within Redis ?

Redis

Ans. SET <KEY_NAME> <VALUE>

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Q1622. Give an example of how Object Oriented Programming Concepts can be implemented.

Design

Ans. You can implement encapsulation in Java by keeping the fields (class variables) private and providing public getter and setter methods to each of them. Java Beans are examples of fully encapsulated classes. Encapsulation in Java: Restricts direct access to data members (fields) of a class.

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Q1623. Can an inner class be subclass of it's parent class ?

Core Java

Ans. Yes that can be done

public class OuterClass {
public class InnerClass extends OuterClass {
}
}

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Q1624. Is this code legal in java i.e nested class within interface implementing the parent interface ?

public interface MyInterface {
public class MyClass implements MyInterface {
}
}

Core Java

Ans. Yes that's legal in java

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Q1625. What are the different types of loops in Java ?

Core Java

Ans. for, while and do while

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Q1626. What is an infinite loop ?

Core Java

Ans. Infinite loop is a programming condition wherein the control goes into an infinite loop because the loop termination condition can never be met. For example -

for(int x=1;x>0;x++){
}

in this loop, with each increment the condition x > 0 will remain true till infinity.

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Q1627. What is a ternary operator ?

Database

Ans. Ternary operator , also called conditional operator is used to decide which value to assign to a variable based on a Boolean value evaluation. It is used as

condition ? value1 : value2

For example

int y = (x > 0) ? x:0; // assign x if it's greater than 0, else assign 0

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Q1628. What is the difference between JDBC, Hibernate and ODBC ?

Database

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Q1629. Is String a Data type in Java ?

Core Java

Ans. String is not a primitive type in java. Anything defined within double quotes like "abc" is an object of String class.

Sample Code for String

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Q1630. Are char,String and Char data types in java ?

Core Java

Ans. char is a primitive data type. String is a class. Char is a wrapper class for primitive char.

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