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Q1741. 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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Q1742. 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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Q1743. 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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Q1744. 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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Q1745. Is it ok to use optional everywhere just to get over nullpointerexception ?

Core Java

Ans. Optional is to be used for arguments / atrributes which are indeed optional i.e the request should continue even if they aren't provided. It should not be used for mandatory attributes or arguments as we would like application to shout out ( with error message / exception trace ) to signify a problem.

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Q1746. Which method will get called if we call it as method(1)

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

Core Java

Ans. Though the call an be bind to either of these but in this case, 1st method will get priority and hence will be called.

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Q1747. 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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Q1748. 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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Q1749. 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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Q1750. 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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Q1751. What is Apache Cassandra ?

Cassandra

Ans. Apache Cassandra is a free and open source distributed NoSQL database management system designed to handle large amounts of data providing high availability with no single point of failure.

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Q1752. 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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Q1753. 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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Q1754. What is Redis ?

Redis

Ans. Redis is an in-memory data structure store, used as a database, cache and message broker.

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Q1755. What happens when you assign a pre initialized reference some other object ?

Core Java

Ans. Now the reference points to a new object in memory. If that was the only reference for the previous object , it will be marked for garbage collection.

Foe example -

Object obj = new Object();
obj = new Object();

object created in first line will be eligible for garbage collection after line 2 as it looses all it's handlers.

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Q1756. 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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Q1757. 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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Q1758. Which of the following is valid greater than and equal to operator in Java ?

>=
=>

Core Java

Ans. >=

=> will result in error.

=> somewhat looks like lambda operator "->"

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Q1759. Java doesn't provide exclusive access to memory like C/C++ and other lower level languages ? What are the advantanges and disadvantages ?

Core Java

Ans. Yes, doesn't provide exclusive access as we cannot allocate and deallocate memory exclusively as Java internally manages it. The advantage of this is that it relieves the coder for such tasks and helps protect from many bugs that may get introduced with imperfect coding. Moreover as java garbage collector collects all unclaimed memory or objects, it helps the application from memory leaks.

On the flip side , as coder doesn't have extensive excess to memory , it is upto java to decide on the state for programming construct and data storage and hence may introduce some security risks. For example - Java keeps string literals in string pool and there is no exclusive way to remove it and hence may stay and sensitive data in string pool may introduce security issues. Moreover when we overwrite a value or object for a variable / reference, it is upto java to purge those values and hence it may stay in memory for a while till java decide that it is no longer referenced and hence should be removed and hence makes it vulnerable for inappropriate access.

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Q1760. What is event handling ? What is event propagation ?

JavaScript

Ans. LinkedIn

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Q1761. What is event bubbling ?

JavaScript

Ans. LinkedIn

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Q1762. Which of following is / are valid static final declaration ?

public static final String MAX_NUM = "10";
public static final Object NULL = null;
public static final MathContext MATH_CONTEXT = new MathContext(2,RoundingMode.CEILING);

Core Java

Ans. All are valid declarations.

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Q1763. Can you name few matchers that can be used with hamcrest assertThat method ?

Junit

Ans. is
not
equals
anyOf
hasSize

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Q1764. What are the benefits of assertThat over assert in Junits ?

Junit

Ans. assertThat is introduced with Junit4 and offers many advatanges over assert. Messages are more explanatory, offer better type safety and are more readable. Moreover hamcrest library is portable as it can used both with junit and TestNG.Moreover assertThat provides flexibility as the same method can be used for assert , assertEquals,assertTrue etc through the use of matcher methods.

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Q1765. What is the use of @Bean annotation in Spring ?

Spring

Ans. There are 2 ways to specify dependencies in Spring, one by the way of specifying beans in config files and other is by specifying annotations like @Bean, @Component , @Service etc to let spring know of the dependencies.

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Q1766. What is a pull request ?

GIT

Ans. It's a facility to shout out your code changes to other collaborators before merging them to the main repository. For example - one may like to have code changes reviewed between his branch and master before merging it to master. So he can open a pull request with the difference between branch and master, get it reviewed and then merge it to master.

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Q1767. What are the different layers of cloud computing ?

Infrastructure

Ans. Paas - Platform as a service
Iaas - Infrastructure as a service
Saas - Software as a service

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Q1768. What is AWS or Amazon Web Services ?

Amazon Web Services (AWS)

Ans. These are the platforms or set of services provided by Amazon for cloud services , database storage , content delivery and other business applications and solutions.

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Q1769. Make the following class immutable

public class Employee {

   private long employeeId;

   private String employeeName;

   public long getEmployeeId() {
      return employeeId;
   }

public void setEmployeeId(long employeeId) {
      this.employeeId = employeeId;
   }

   public String getEmployeeName() {
      return employeeName;
   }

public void setEmployeeName(String employeeName) {
      this.employeeName = employeeName;
   }
}

Core Java

Ans. public class Employee {

   private long employeeId;

   private String employeeName;

   public Employee(long employeeId,String employeeName){
      this.employeeId = employeeId;
      this.employeeName = employeeName;
   }

   public long getEmployeeId() {
      return employeeId;
   }

   public long getEmployeeName() {
      return employeeName;
   }
}

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Q1770. What is the difference between reference and object ?

Core Java

Ans. Object is an entity in Java , i.e which has a state ( instance variables ) and methods attached to it ( static or non static , through class definition ). References are the identifiers that are used to point to objects.

For example -

Employee emp = new Employee();
emp = new Employee();

In this code, emp is the reference that gets assigned to the new object created by the new operator. In the second line , we have assigned the same reference to another object. So with these 2 lines of code, we have 2 objects in memory with reference emp now pointing to second object.

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