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

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Q211. Which of the following doesn't extend Collection interface ?

a. Set
b. List
c. Map
d. Queue

Core Java

Ans. Map

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Q212. Which of the following Java feature promotes Code Re usability ?

a. Abstraction
b. Encapsulation
c. Inheritance
d. Polymorphism

Core Java

Ans. Inheritance

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Q213. enums are intrinsically ..

a. private
b. public
c. static
d. final

Core Java

Ans. static

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Q214. What will happen if we don't have termination statement in recursion ?

Ans. Function call allocates a stackframe in stack. Every stackframe will use some memory to store local variables, parameters and to remember return address. Without terminating condition stackframes will keep consuming memory from stack and eventually program will result in stackoverflow error.

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Q215. In which cases , moving methods to utility class could be useful ?

Core Java

Ans. It could be worthy to move a method to util class if the method needs to be shared, doesn't require polymorphic behavior and need not be overridden in special cases.

Don't belong to one group through is-a relationship ( You can share through parent class method )

Don't implement a specific interface ( java 8 default methods )

Doesn't involve complex computing as you will be loosing the benefit of object state with just static method.

Doesn't require polymorphic behavior as static methods don't participate in runtime polymorphism.

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This question can be asked in different variants like performace improvement of an application, improving performance for DB communication etc.

Q216. What are the ways in which execution time of the code can be improved ?

Solution

Ans. This depends on entirely upon the code type. For example

1.If its just logic, we can try it to short circuit or put the if / switch case with maximum probability in the beginning.

2. Can use faster data structures, for eg - random retrieval instead of sequence / iterator

3. Working with primitive types or even bytes instead of Objects, even though it may result in marginal improvement.

4. If its service call, then service call with bulk load can help

5. If DB Operation, then with use of Indices , Views or using ORM , cache etc.

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Q217. Difference between GET and POST Requests ?

Web Service

Ans. GET is supposed to get information from the server. Client sends the minimal information so that Server can respond with the response body on basis of request. For example - You want to get complete employment record for employee id 123

POST is supposed to send the information for submission. Payload or a Body is usually sent so that it can be persisted on the server. For example - Sending the complete information of an employee ( id, name , dept etc ) to the server for persisting it.

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Q218. How do you resolve Maven Dependencies issue while upgrading dependencies versions ?

Maven

Ans. Step 1 - Upgrade the required dependency , perform build and check build errors

Step 2.1 - If the error is of missing transitive dependency ( which is rare and means that the previous version has a dependency which is missing in the later version ), I would look for the dependency in google and hence will include it as direct dependency in Pom file.

Step 2.2. If the error is for Duplicate dependencies , and the choice is between transitive and direct dependency, I usually remove the direct dependency.

Step 2.3 - If the error is for Duplicate dependencies , and both are transitive dependencies. I first make a choice ( usually later version ) and then ignore the previous version dependency.

Step 2.4 - If the error is for Duplicate dependencies , and there are more than 2 duplicates, I usually ignore it by specifying within maven-enforcer-plugin config.

Step 3 - Perform a Clean Build.

Step 4 - Check Maven Dependency Tree to make sure that Duplicates have been removed or dependency is there in case of missing dependency.

Step 5 - Perform tests and make sure that there are no runtime problems.

Step 6 - If there are runtime problems ( which very likely occurs if you have different version dependencies , very likely by doing 2.4 , you will have to remove step 2.4 and alternately perform 2.2 or 2.3 )

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Q219. What is coupling and Cohesion ?

Design

Ans. Coupling is the degree of interdependence between software modules, a measure of how closely connected two modules are or the strength of the relationships between modules.

Cohesion refers to the degree to which the elements of a module belong together. Cohesion measures the strength of relationship between pieces of functionality within a given module.

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Q220. Design a Data Structure for a full text Search ?

Design

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

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Q221. Write a Program to reverse a Linked List ?

Data Structure

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

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Q222. What are different types of variables a class can have ?

Core Java

Ans. 1. Method local variables - These are declared and defined within a method ( instance or static methods ) and their scope is limited to the method itself. They are destructed once the execution of method completes. They are stored in stack memory.

2. Instance variables - These are declared as non static variables as part of the class.They are initialized as part of object creation ( constructor ) and are destructed by java's garbage collection mechanism and hence stored in heap.

3. Static variables - These are declared with the static keyword and are part of the class. They are initialized at the time of class loading and are destructed by java's garbage collection mechanism and hence stored in heap.

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Q223. Why java doesn't support multiple Inheritance ?

or

Explain Java Diamond Problem.

Core Java

Ans. class A {
void test() {
System.out.println("test() method");
}
}

class B {
void test() {
System.out.println("test() method");
}
}

Suppose if Java allows multiple inheritance like this,

class C extends A, B {
}

A and B test() methods are inheriting to C class.

So which test() method C class will take? As A & B class test() methods are different , So here we would Facing Ambiguity.

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Q224. Design an app to find 10 most visited urls

Core Java

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

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Q225. Trim a string without using String library method

Core Java

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

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Usually asked to entry level software developers.

Q226. Write a program to swap two variables without using third

Core Java

Ans. public static void main(String[] args) {
   int num1 = 1;
   int num2 = 2;
   num1 = num1^num2;
   num2 = num1^num2;
   num1 = num1^num2;
   System.out.print("num1 = " + num1 +", num2 = "+num2);
}

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Q227. Write a Program to print pattern like following

*
**
***
****
*****
*****
****
***
**
*

Core Java

Ans. public class BuggyBread {
   public static void main(String args[]) {
      for(int x=1;x<=5;x++){
         for(int y=1;y<=x;y++){
            System.out.print("*");
         }

         System.out.println("");
      }

      for(int x=5;x>=1;x--){
         for(int y=1;y<=x;y++){
            System.out.print("*");
         }

         System.out.println("");
      }
   }
}

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Q228. If an Abstract class has only abstract methods, What's the difference between such a class and an interface ?

Core Java

Ans. Such a class still can have member elements which can be inherited and hence facilitate code reuse. Moreover Abstract class can have non final static elements whereas interfaces are only allowed to have static final elements.

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Q229. Can we overload method as following ?

void method(int... x){};
void method(int[] x){};

Core Java

Ans. No. Because java internally treats var args as arrays and hence both method declarations will generate the same byte code and hence would result in ambiguity while determining call binding.

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Q230. What is the difference between single instance Web environment and Load Balanced Auto Scaling ?

Amazon Web Services (AWS)

Ans. Single instance means there is only 1 instance that will bear all the traffic load whereas Load balanced server means that there will be a cluster of servers that will host the application and load will be balanced distributed among them. Auto Scaling means that the number of instances will be expanded / shrunken based on the rule. Rule could be the traffic count , response time etc.

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Q231. What does import java.util.* means in java ?

Core Java

Ans. It means import all the classes and interfaces within java.util package and make them available to use within the current class or interface. This is shorthand wild card annotation for importing all classes within a particular package. This won't import the classes within the sub packages of java.util.

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Q232. What are the benefits of Dependency Injection or IOC ?

Design

Ans. Central place for configuring dependencies.

No need to create object, container manage all this By using Run time polymorphism and association.

Facilities development of framework / libraries by injecting implementation classes in the implementation code.

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Q233. If you need to consume messages from the queue faster, which approach will you recommend - batching or concurrency ?

Design

Ans. Each has it's own advantages

Batching requires less resources but may result in loosing whole batch in case of failure whereas concurrency even though is little more expensive in terms of resources but would result in minimal loss in case of failure.

In case messages are to be consumed in a particular order, batching them in that order and then consuming them makes better sense.

if incoming messages are not continuous , it makes more sense to do concurrency as we need not wait for all messages to form a batch and flush. Though time sensitivity can be added but that would add unnecessary complexity.

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Q234. When we say final x = 10, is the reference final or the value ?

Core Java

Ans. final keyword have meaning only to referenced and not the value. It means that the specified reference cannot be dereferenced. It doesn't control the value assigned to the memory that's being referenced. This is the reason that final object references doesn't mean that the object is immutable but means that the reference cannot be changed to point to new object.

In case of primitive types too, when we assign a reference to another, values are passed and not the object reference, and hence a new placeholder is created in memory with the same value. That is why final to that context means that you cannot change the assigned memory and there is no way we can have that memory place have another value.

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Q235. What is the difference between Singleton and Prototype Bean scope in Spring ?

Spring

Ans. Prototype scope - A new object is created each time it is injected/looked up. It will use new SomeClass() each time.

Singleton scope - It is the default scope. The same object is returned each time it is injected/looked up. Here it will instantiate one instance of SomeClass and then return it each time.

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Q236. What is the difference between uninitialized values for primitive types and Wrapper classes ?

Core Java

Ans. When we create reference for primitive type, it's memory is allocated. So even if we don't assign any value to it, the default value is initialized.

int x; // default value 0 initialized

But for object references, it's different as references hold nothing till an object is assigned.

Object obj; // contains null

So all primitive types when declared , contains their respective default values on the basis of their type whereas all wrapper class References contains null irrespective of their types.

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Q237. What is the use of Object class ?

Core Java

Ans. 1. Default definition for some of the methods , like equals, hashcode etc that gets carried to all objects even if you don't define anything. But that default definition is kind of like assigning 0 to integer, it just provide a safe state , nothing much for comparison.

2. Places where you have no idea about what object you may receive and just want to perform out of 8 basic methods of object class, something like printing their string representation ( defined by their toString method ), or equality ( using their equals method )

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Q238. What is cloud computing ?

Cloud Computing

Ans. Cloud Computing is a way of using IT infrastructure with following traits -

1. On Demand Infrastructure
2. Broad Network Access
3. Resource Pooling
4. Rapid Elasticity
5. Measured Service

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Q239. What are the services provided by AWS ?

Amazon Web Services (AWS)

Ans. AWS provides various types of services like Computing ( EC2 , Lambda , EKS ), Storage ( S3, Glacier ), Database ( RDS , DynamoDB ), Streaming ( Kinesis ), Queue ( SQS ), Security and Access ( IAM ) etc.

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Q240. What are the problems one could face while working with serverless technologies like AWS Lambda ?

Amazon Web Services (AWS)

Ans. Warm up time for certain technologies like Java ( JVM Warmup )

Performance

Size of Deployable ( Bigger size packaging should go in S3 )

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