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

Interview Questions and Answers - Order By Newest

Q571. What is the difference between constructor and instance initialization blocks ?

Ans. Constructor has the same name as class name whereas instance initialization block just have a body without any name or visibility type.

instance initialization blocks are useful if we want to have some code run regardless of which constructor is used or if we want to do some instance initialization for anonymous classes.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve instance initialization blocks constructor constructor vs instance initialization blocks Asked in 2 Companies}

Try 1 Question(s) Test

Q572. Is this code legal in Java ?

public class BuggyBread {
{
System.out.println("HelloWorld.");
}
}

Ans. Yes, It's an instance initialization block.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve code instance initialization block}

Try 1 Question(s) Test

Frequently asked question in companies using Rest Web services.

Q573. Different between POST and PUT in Rest

Rest

Ans. PUT requests are only meant to place the object as it is on server. For example - You want a file to be uploaded and then placed in a particular folder or you want an Employee object to be persisted in the table.

POST requests are also meant to transfer information from client to server but that information once received at the server is evaluated , modified or refactored before persisting.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Put vs Post Rest Asked in 5 Companies frequent}

Q574. Should a DB Insert Request be a POST or PUT request in Rest

Rest

Ans. It depends on whether the request object is persisted as it is

or

its first dismantled, modified or refactored and then inserted into DB.

In first case, it should be a PUT request whereas in second case it should be a POST Request.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Put vs Post Rest Asked in 2 Companies intermediate frequent}

Rarely asked as it was introduced with Java 8.

Q575. What is the use of :: operator wef from Java 8 ?

Core Java

Ans. We can refer to a function using this operator like System.out.println(intList.stream().reduce(Math::max).get());

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve :: operator lambda expression java 8}

Q576. What is Hot Deployment ?

Server

Ans. It is the ability to deploy changes on the fly without need to first build , deploy and then restart. All these functions happens on the fly as soon as the changes are made to the code.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve hot deployment deployment container application server production support}

Q577. Difference between Hot and Cold Deployment ?

Server

Ans. Cold Deployment is a conventional deployment mechanism that follows the multi step process to deploy code changes to the running app i.e Build -> Deploy - Restart.

whereas

Hot Deployment is deployment changes on the fly without need to first build , deploy and then restart. All these functions happens on the fly as soon as the changes are made to the code.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Hot deployment cold deployment application server production support}

Q578. What is wrong with the following if statement ?

if(x==y && x.equals(y) {
}

Core Java

Ans. x==y means that both references have same type and are pointing to same memory location and hence would always mean that they have same value.

x.equals(y) is not required in this case.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve if statement control statements == and equals == .equals code optimization}

Try 2 Question(s) Test

Q579. What is wrong with the following if statement ?

if(x==y || x.equals(y) {
}

Core Java

Ans. if x==y turns out to be true x.equals(y) will be true too. If x.equals(y) could be true even if x==y is true or not.

So the only possible outcomes are

1 || 1 = 1
0 || 1 = 1
0 || 0 = 0

i.e the outcome of x.equals(y)

check for x==y is not required in this if statement.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve if statement control statements == and equals == .equals code optimization}

Try 1 Question(s) Test

Q580. Does it make sense to clone an object which is supposed to be immutable ?

Design

Ans. It make sense only if we intend to modify either of the object and would like to preserve original state in other. Otherwise we can reuse the original object by making it singleton.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve clone clone objects prototype design pattern immutable immutability immutability cloning}

Q581. Can we access private members of the parent class ? i.e Are private members of the class visible in the derived class ?

Core Java

Ans. No, If both Parent and Derived are outer classes.

public class Vehicle {
private static String manufacturingDate = "2016";
}

public class Car extends Vehicle{
public static void main(String args[]){
System.out.println(manufacturingDate); // error - The field Vehicle.manufacturingDate is not visible
}
}

Yes, If derived is the inner class of Parent.

public class Vehicle {
private static String manufacturingDate = "2016";
static public class Car extends Vehicle{
public static void main(String args[]){
System.out.println(manufacturingDate); // no problem
}
}
}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve private members private methods private variables inheritance object oriented programming (oops) oops concepts members visibility inner classes nexted classes basic frequent}

Q582. What is a classpath in Java ?

Core Java

Ans. Classpath is the parameter for JVM to look for java classes ( .class files ) that are to be looad by class loader

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve classpath Asked in 1 Companies basic}

Q583. Write a class explaining builder pattern ?

Design

Ans.

public class BuggyBread { 



   private String element1; 



   private String element2; 



   private BuggyBread(String element1, String element2){ 

      this.element1 = element1; 

      this.element2 = element2; 

   } 



   public static class Builder { 

    

      private String element1; 



      private String element2; 



      Builder(BuggyBread buggybread){ 

         element1 = buggybread.element1; 

         element2 = buggybread.element2; 

      } 



      Builder withElement1(String element1){ 

         this.element1 = element1; 

         return this; 

      } 



      Builder withElement2(String element2){ 

         this.element2 = element2; 

         return this; 

      } 



      BuggyBread build(){ 

         BuggyBread buggybread = new BuggyBread(element1,element2); 

         return buggybread; 

      } 

   } 

}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve builder pattern builder class}

Try 1 Question(s) Test

Q584. What is the difference between = and == in Java ?

Core Java

Ans. = is the assignment operator that assigns the result of the expression on the right to the variable on the left, whereas

== is the operator to check object equality to see if the reference on left and right are pointing to the same object. For primitive types, its used to check if both variables holds the same value.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve = == assignment operator object equality difference between Basic}

Q585. How is == operator different for objects and primitive types ?

Core Java

Ans. For objects or references, == operator check if the reference on left and right points to the same object.

For primitive types or variables, == operator check if the variable on left and right holds the same value.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve == object equality operator Basic}

Q586. What are the benefits of Enums ?

Core Java

Ans. Enums in Java are used to declare predefined objects and then reuse them. they offer many benefits

1. Enum instance are type safe and thread safe.

2. Enum instances are singleton and hence reused.

3. If we use Enums with Switch , It makes sure that the passed argument is either of its instance and hence provides a safeguard.

4. If we use Enum with Sorted Collections we can sort the elements with a predefined priorities ( as per constant declaration in enum )

5. We can use Enum as a Factory by defining its constructor.

6. We can store related constant data within enum. For example - If we know the values for the map upfront, we can alternatively use an enum.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Asked in 6 Companies}

Q587. Have you heard of Ban Duplicate Classes Maven enforcer plugin ? What is its use ?

Maven

Ans. Yes , we have been using this plugin with our projects and its purpose is to warn and stop the Build if there are duplicates of the same package and class are being carried either directly or through transitive dependencies. the duplicate could be coming through different types of dependencies or through different versions of the same dependency. Its purpose is to make sure that there is only one copy thats being used at compile time and runtime and hence shouldnt later result in runtime problems.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve maven ban duplicate classes enforcer plugin}

Q588. How to tackle duplicate classes in maven build ?

Maven

Ans. The simplest way is to ignore them if Maven enforcer plugin is complaining about it but it may lead to runtime problems later.

We can do the dependency:tree to see from where these duplicate ones are coming and hence can exclude the duplicate one.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve maven ban duplicate classes enforcer plugin}

Q589. Explain what happens when insertion is performed in case of ArrayList and LinkedList.

Data Structure

Ans. Array List works on Array and when we add an element in middle of the list, Array List need to update the index of all subsequent elements. I the capacity is full, it even may need to move the whole list to a new memory location . Linked List works on Double linked list algorithm and all it has to do is to adjust the address of the previous and next elements.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve arraylist vs linkedlist collections list Asked in 2 Companies}

Q590. How to Bulk upload the data into Oracle database?

Database

Ans. We can use external table feature of Oracle.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Asked in 1 Companies Intermediate}

Frequently asked Design Pattern interview question.

Q591. What is a prototype design pattern ?

Design

Ans. The prototype pattern is a creational design pattern. It is used when the type of objects to create is determined by a prototypical instance, which is cloned to produce new objects. Prototype is used when we need duplicate copies of objects.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve design pattern prototype design pattern cloning Asked in 11 Companies intermediate}

Q592. Write an SQL Statement to add a foreign key constraint in oracle ?

Database

Ans. ALTER TABLE <Table_Name> ADD CONSTRAINT <Constraint_Name> FOREIGN KEY (<Column_Name>) REFERENCES <Foreign_Table>(<Foreign_Column>);

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve database add foreign key constraint}

Q593. What does the web status code 404,500 and 200 mean ?

Java EE

Ans. 404 means the resource is not found on the server.The resource might not be deployed correctly.

500 means internal server error which means that resource was located but then it resulted in some exception or error.

200 means Ok.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve web status code Asked in 1 Companies}

Try 1 Question(s) Test

Q594. What is Dirty read in Database Transactions ?

Database

Ans. A dirty read occurs when a transaction is allowed to read data from a row that has been modified by another running transaction but not yet committed.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve database transaction Asked in 8 Companies}

Q595. Have you ever felt the need of keeping the constructor private ?

Design

Ans. Yes, When either we don't want an object to be created ( class having all static elements and hence not required ) or object to be created using a static method or static block. One such example could be a situation when we would like app to load objects at start up and we would like to restrict new object creation by any request.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve private constructor constructor}

Usually asked with Questions related to Generics.

Q596. What are Type Erasures in Java ?

Core Java

Ans. Type erasure applies to the use of generics. When generics are used, they're pre compiled into compile time checks and execution-time casts.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve type erasures generics Asked in 2 Companies intermediate rare}

Q597. How can one determine if JVM is 32-bit or 64-bit from Java Program ?

Core Java

Ans. There is a Java system property "sun.arch.data.model" that can tell if JVM is 32 bit of 64 bit

System.getProperty("sun.arch.data.model") can be used to get that property.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve jvm intermediate rare}

Q598. Why calculations in float or Double sometimes gives unpredictable results ?

Core Java

Ans. Because the way float values are stored its not precise.

For example - 0.1 is actually stored as
0.1000000000000000055511151231257827021181583404541015625

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve double float data type basic frequent}

Q599. What is Java NumberFormatException ?

Core Java

Ans. NumberFormatException is the exception that Java throws when we try to convert one data type to the Number data type but the value is not parsable to be a Number.

For example , the following code will result in the NumberFormatException

String string = "Buggy";
int strtoInt = Integer.parseInt(string);

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve exceptions NumberFormatException}

Q600. How Spliterator in Java 8 different than iterator ?

Core Java

Ans. Though there are many differences the way internally they both iterates the collections and streams respectively, but the main difference in performance that is achieved by spliterator as it can iterate Streams in Parallel whereas iterator only iterates collections sequentially.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java8 java 8 spliterator java 8 streams streams}

Search Interview Questions

Help us and Others Improve. Please let us know the questions asked in any of your previous interview.