Interview Questions and Answers for 'OLA' | Search Interview Question

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Q31. When do we generally get the database error - Unique Constraint Violated ?

Ans. This error can result either on an insert, update or delete when any change in data results in duplicate record or subset of it having unique constraint on record or its subset. For example - If we have a unique constraint on a combination of columns and then trying to insert duplicate column values.

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Q32. When should we use Abstract classes ?

Core Java

Ans. Abstract classes provide a mechanism of interfacing ( using abstract method ) as well as inheritance ( extending abstract class ). So they should be used in place of interfaces in case there is some code ( methods ) or object body ( member elements ) that can be reused with inheritance.

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Q33. Write a program in Java that prints the numbers from 1 to 100. But for multiples of three print Fizz instead of the number and for the multiples of five print Buz. For numbers which are multiples of both three and five print FizzBuzz

Core Java

Ans. public class Class{
public static void main(String[] args){
for(int i=1;i<= 100;i++){
if(i%3 == 0){
if(i%5 == 0){
System.out.println("FizzBuzz");
}
System.out.println("Fizz");
} else if(i%5 == 0){
System.out.println("Buzz");
} else {
System.out.println(i);
}

}
}
}

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Q34. What do you make out of this error

org.hibernate.exception.ConstraintViolationException: could not insert: [<Entity>]
Caused by: java.sql.SQLIntegrityConstraintViolationException: ORA-00001: unique constraint (<Constraint Name>) violated

and how would you go about debugging it ?

Database

Ans. Application is unable to insert a record as it violates a unique constraint.

The exception states the constraint and Table can be located by the Entity mapping. So I will go to the DB and will first check to which all columns the unique constraint applies. And then I will go and check the code and logs to see how come the duplicate column values were attempted to be inserted when they were not supposed to be.

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Q35. What is ConstraintViolationException in Hibernate ?

Hibernate

Ans. The exception is thrown when a database constraint is violated.

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Q36. 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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Q37. Will the following code compile ?

final HashMap hm = new HashMap();
hm.put("Ravi", 221);

Core Java

Ans. Yes, it will compile without error. final in this context means that the reference hm cannot be assigned to a new hash map but didn't restrict from changing the state of collection already held by hm.

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Q38. How can i split a linked list in two parts in java 8?

Core Java

Ans. This can be done using a Spliterator.

LinkedList list = Arrays.asList("names","numbs","birds","animals");
Spliterator split1 = list.Spliterator();
Spliterator split2 = split1.Spliterator();

Now, the LinkedList is split into split1 and split2.
use split2 first then split1 to check the output.

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Q39. Difference between Arrays and LinkedList ?

Data Structure

^{This question was recently asked at 'Spillman Technologies,Motorola Solutions'.This question is still unanswered. Can you please provide an answer.}

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Q40. What is your role in current project ?

General

Ans. Possible Answer - Java Developer

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Q41. Why do you want to leave your current job ?

General

Ans. The most effective and acceptable reasons for leaving your current job should be positive e.g. moving forward in your life or career

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Q42. how is the internal code for the "volatile" implemented ?

Core Java

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

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Q43. What are the different ways to avoid multi Threading related problems in Java ?

Core Java

Ans. Synchronization,
Concurrent classes,
Volatile keyword,
Implementing concurrent Lock interface,
Immutable classes

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Q44. Can we make array volatile in Java ?

Core Java

Ans. Yes, you can make an array (both primitive and reference type array e.g. an int array and String array) volatile in Java but only changes to reference pointing to an array will be visible to all threads, not the whole array

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Q45. Have you heard of volatile Table in Teradata ?

Teradata

Ans. If you create table with VOLATILE option, the life of the table will be only for the current session.
It will be automatically dropped by Teradata manager once session expires.

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Q46. Difference between Query param and path param ?

^{This question was recently asked at 'GSpann Technologies, Motorola Solutions'.This question is still unanswered. Can you please provide an answer.}

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Q47. Explain memory leaks and how to prevent them.

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

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Q48. Explain Rest architecture

Rest

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Q49. How do you achieve String immutability ?

Core Java

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Q50. What is SNMP ?

Networking

Ans. SNMP or Simple Network Management protocol is an application layer protocol for exchanging management information between network devices.

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Q51. What is interpolation in Angular ?

Angular

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Q52. Can we use interpolation with all data types ?

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Q53. What are the limitations with using interpolation ? Why do we need property binding ?

Ans. Interpolation can only work with String types and hence we need property binding while working with other data types.

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Q54. The use of volatile keyword facilitates ..

Core Java

a. Making Use of Cache for better Performance

b. Avoiding use of Cache

c. Making use of Backward as well as Forward Cache

d. Keeping only one copy of variable in Cache

Ans.b. Avoiding use of Cache

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