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Q391. 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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Q392. 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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Q393. 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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Q394. What is Boxing conversion ?

Core Java

Ans. Boxing conversion converts expressions of primitive type to corresponding expressions of reference type.

For example

boolean to Boolean
long to Long
double to Double

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Q395. What is widening and narrowing conversion in Java ?

Core Java

Ans. Conversion means that the expression / literal / value of one type getting converted to other type.

Widening conversion is the conversion from Type A to Type B where B requires a wider space than A. For example - int to long, float to double, char to String etc. As the value moves to a wider space, there is no loss of information.

Narrowing conversion is the conversion from Type A to Type B where B requires a narrower space space than A. For example - int to long, float to double, char to String etc.As the value moves to a narrower space, there is a loss of information.

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Q396. What is AWS CloudWatch ?

Amazon Web Services (AWS)

Ans. Amazon CloudWatch is a monitoring service for AWS cloud resources like Beanstalk and DB instances. We can use CloudWatch to monitor the state of resources, collect metrices, set alarms and appropriate response to the alarm state.

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Q397. How do you check logs for your application in AWS ?

Amazon Web Services (AWS)

Ans. We can do it by either going to Elastic Beanstalk -> Respective instance -> Logs

or using CloudWatch -> Logs -> Respective Log Group

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Q398. What is the difference between latency, response time and processing time ?

Web Service

Ans. Latency is the delay incurred while communicating a message i.e the time took the message in transit over network.

processing time is the delay it took for the server to process the request.

Response time is the sum total of latency and processing time.

For example -

Let's say it takes 1 ms for the request to reach from client to server and similar 1 ms for the response to come back to client. Moreover it takes approx 10 ms for the application to process the request. So The response time would be outward latency + processing time + inward latency = 12 ms

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Q399. What is Amazon EC2 ?

Amazon Web Services (AWS)

Ans. Amazon Elastic Compute Cloud or EC2 provides scalable computing capacity in the AWS cloud. It can be used to create Virtual Environments , storage and configure. EC2 enables to upgrade or downgrade infrastructure according to the rules defined ( with fluctuation in latency, traffic etc )

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Q400. What is dynamic dispatch in Java ?

Core Java

Ans. Dynamic dispatch in java is also known as runtime polymorphism.It is a process in which a call to an overriden method is resolved at runtime.

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Q401. Write a Program to delete a node from Linked List ?

Data Structure

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

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_{Like Discuss Correct / Improve linkedlist delete a node from linked list Asked in 1 Companies}

Q402. How do you take screenshot in selenium?

Selenium

Ans. TakeScreenshot th = TakeScreenshot(driver); //Enable the driver object to take screenshot

File src = th.getScreenShotAs(OutputType.FILE);

FileUtils.copyFilesrc("locationWhereUWantToPlaceTheScreenshot.jpg");

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Q403. What is the order in which triggers gets fired ?

Database

Ans. There is no specific order in which database fires the triggers if they are for the same operation. If we need to have a specific order for their execution, we should have them all in a stored procedure and the procedure should get executed upon the event.

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Q404. What is a host file ?

Operating System

Ans. It's an operating system file that maps IP address to host names. The hosts file assists the OS in addressing networked components and serves the function of translating human friendly hostnames into numeric protocol addresses, called IP addresses, that identify and locate a host in an IP network.

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Q405. Do you prefer using var args ?

Core Java

Ans. Though var args are used rarely but they are pretty useful if a method is expected to receive variable number of arguments. For example - it's pretty useful for the main method as the caller has the flexibility to provide arguments in infinite ways.It provides a convenience and flexibility to the caller.

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Q406. What is the difference between these two method declarations ?

private static void method(String[] arg)

and

private static void method(String... arg)

Core Java

Ans. First expects the argument as a string array whereas second expects variable number of string arguments or a string array.

So we can call both by providing string array as an argument but second can be called with 0 to n string arguments which cannot be done for first.

for example - We can call second method with any of following

method();
method("Hello");
method("Hello","World");
method(new String[4]);

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Q407. Will this code work

public class BuggyBread {

   public static void main(String[] args) {
      method("Hello","World");
   }

   private static void method(String[] arg){
      System.out.println(arg);
   }
}

What all possible changes we can make to method signature to make it work ?

Core Java

Ans. It won't work as java won't find the method definition for method with 2 arguments.

We can either declare the method as

private static void method(String arg,String arg2)

or

private static void method(String... arg)

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Q408. Do you see any problem with this code

public class BuggyBread {

   public static void main(String[] args) {
      method("Hello");
   }

   private static void method(String... args){
      for(String arg:args){
         System.out.println(arg);
      }
   }

   private static void method(String[] arg){
      System.out.println(arg);
   }
}

Core Java

Ans. Yes, it will give compilation error and java will complain about duplicate method. Java treat var args internally as arrays and hence would result in same byte code for both method's syntax.

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Q409. Do you see any problem with this code

public class BuggyBread {

   public static void main(String[] args) {
      method("Hello");
   }

   private static void method(String... args){
      for(String arg:args){
         System.out.println(arg);
      }
   }

   private static void method(String arg){
      System.out.println(arg);
   }
}

Core Java

Ans. It will compile fine and the method call will bind to method with specific argument and not with var arg

i.e private static void method(String arg)

It will print "Hello" upon execution

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Q410. Do you see any problem with this code

public class BuggyBread {

   public static void main(String[] args) {
      method();
   }

   private static void method(String... args){
      for(String arg:args){
         System.out.println(arg);
      }
   }
}

Core Java

Ans. This will compile fine as we can provide 0 arguments for a var arg but will print nothing upon execution.

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Q411. Do you see any problem with this code

public class BuggyBread {

   public static void main(String[] args) {
      method("Hello","World");
   }

   private static void method(String... args){
      for(String arg:args){
         System.out.println(arg);
      }
   }
}

Core Java

Ans. No, It will compile and execute perfectly fine. As we are using method with var args , we can call it with 0 to n arguments.

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Q412. Can we catch errors in Java ?

Core Java

Ans. Yes we can

try {
// code
} catch (Error ex) {
// handling code
}

but we shouldn't ideally do that as errors are mostly JVM based and not application based and there is rarely we can do something about it. Very likely catching and not re throwing would lead to muting their response or trace.

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Q413. 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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Q414. Why following method declarations are not valid ?

void method(int... x, int y){};
void method(int... x,int... y){};

Core Java

Ans. Because var args are not only allowed with the last argument in the method declaration.

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Q415. Which of the following are valid declarations

1. void method(int... x){};
2. void method(int.. x){};
3. void method(int.. .x){};
4. void method(int ...x){};
5. void method(int... x){};
6. void method(int ... x){};
7. void method(int x, int... y){};
8. void method(int... x, int y){};
9. void method(int... x,int... y){};

Core Java

Ans. 1st is a valid and standard declaration.

2nd results in compilation error as only 2 dots are there.

3rd results in compilation error as three dots are not consecutive and broken.

4 through 6 may not be standard and ideal way of declarations but they are valid and will compile and work fine.

7 is valid declaration.

8 and 9 will result in compilation error as var args can only be provided to last argument.

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Q416. What are var args ?

or

What is the use of var args ?

Core Java

Ans. Var args is the feature of Java that allows a method to have variable number of arguments. Var args are used when we are not sure about the number of arguments a method may need. Internally java treats them as array.

Declarations of methods with var args

void method(int... x){};
void method(int x, int... y){};

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Q417. What is the difference between Oracle , Cassandra and Redis ?

Database

Ans. Oracle is a relational database. Cassandra is a noSQL Database whereas Redis is an inmemory cache.

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Q418. What is replication in Redis ? why do we need it ?

Redis

Ans. Asynchronous Replication of information from master to all slaves. Redis is an in memory storage and hence any crash may result in complete loss of information on a cluster.

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Q419. Is it necessary to specify "employeeId" with @PathParam("employeeId") in this case,

@Path("/{employeeId}")
public String employeeInfo(@PathParam("employeeId") Long employeeId){
}

Rest

Ans. No, it's optional as the name of path param required is same as method param name in this case.

Even the declaration as following should work -

@Path("/{employeeId}")
public String employeeInfo(@PathParam Long employeeId){
}

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Q420. If given a choice , which one would you prefer to send params to the Get service , path params or query param ?

Web Service

Ans. If the number of params is quite large , I would prefer to either split it with majority of it in query params or all in query params.

If the params are all mandatory , I would keep it as path params. If it's optional , I would keep it as query param so as to keep consistent base url.

If we don't require the param name , then they can be kept as path params as query params necessitates the usage of param name.

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