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Q631. 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);
   }
}

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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Q632. 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 ?

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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Q633. What is the order in which triggers gets fired ?

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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Q634. What is widening and narrowing conversion in 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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Q635. Difference between Load Balancing and Failover Clustering ?

Ans. Load Balancing is a provision to improve performance by reducing load on a single machine / server. Traffic or load is distributed among different machines and hence resulting in better performance / response time by leveraging more resources.

Failover is a provision to achieve better availability by switching to a backup server in case of failure.

Load Balancing aims as improving performance whereas failover aims at improving availability.

We can achieve both together by using a Load Balancing system which will isolate an instance in case of it's failure.

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Q636. How can we hide a class in Java ?

Ans. By encapsulating it within another class and declaring it private. In such a case, it will only be accessible through parent class or parent class object.

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Q637. How would you explain the statement "Java Programs are collection of objects" ?

Ans. Java Programs are collection of objects that communicates with each other to get a task accomplished. To add to those objects, there are common spaces ( static i.e common for objects belonging to a class ) that are used too.

We can visualize objects as departments of an organization in real world. Just like Task gets initiated in one department and then files are moved across different departments to get work done. In a similar fashion, a task is initiated in one object ( having main method ) and then information ( through POJOs / DTOs ) is moved across objects to accomplish a task.

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Q638. Why iterators of an array list are fail fast ?

Ans. Because it's access isn't synchronized and hence access / modification by multiple threads may lead to inconsistent state.

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Q639. What problem we could have with ArrayList which aren't possible with Vectors ?

Ans. ArrayLists aren't synchronized and hence doesn't allow synchronized access. As multiple threads can access an arraylist in parallel, it may result in an inconsistent state.

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Q640. What is the quickest way to find count of duplicate elements in an arraylist, without using iteration or loops ?

Ans. We can copy the elements to a Set and then find the difference of count between ArrayList and Set. As Set don't allow duplicates , they will be removed in the set.

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Q641. Write a Program for insertion sort.

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

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Very frequently asked. Usually among very first few questions.

Q642. Define encapsulation in Java ?

Ans. Encapsulation is a feature of OOP's that binds the data and it's associated methods together as a single unit and facilitate protection and data hiding by providing minimal interface to outside. For example - member variables are declared private and are accessed through public methods. Moreover we have private methods that can only be used internally and hence providing minimal interface to outside class through use of public methods.

Sample Code for encapsulation

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Q643. What is the relationship between shard and partition key in kinesis stream ?

Amazon Web Services (AWS)

Ans. A partition key is used to group data by shard within a stream. A partition key identifies which shard the message belong to.

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Q644. Solve the producer and consumer problem

Operating System

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

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Q645. What do you understand by "Scaling Trigger" ?

Ans. It's a configuration for auto scaling environment that specify the attributes / conditions for scaling instances up and down. For example - We may like environment to scale up when the number of requests / sec increases a particular threshold and scale down when it decreases below a threshold.

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Q646. What is the difference between "Manual Scaling" and "Auto Scaling" ?

Ans. Manual scaling is the process of scaling instances up and down in a an enviornment manually by observing the scaling trigger whereas Auto scaling is the process wherein a Trigger condition specified as a scaling trigger will trigger scaling up and down of instances.

for example - If an organization has a policy of scaling up if requests / sec / instance exceeds 10000, Operations team will have to manually monitor the metric and they can request scaling up and down as the need arise. Manual scaling offers flexibility as team can scale on the basis of combination of factors and can take decision on flyby requires continuous monitoring.

The same trigger can be fed as triggering policy to the environment and can be taken care by the system. This requires availability of such triggering policy within the environment configuration but as it's automatically handled, requires no supervision.

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Q647. Can we compile and execute a Java class without main method ?

Ans. No without main method can not be executed it will throw an error illegal start of type. Main method is the entry point of application.

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Q648. What is the purpose of re throwing the exception when we can provide the handling at the first catch itself ?

Ans. Sometimes the calls move across layers of classes and functions and hence each layer needs to perform some function like cleaning if something goes wrong deep inside.

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Q649. Can a source file contain more than one class declaration ?

Ans. Yes, but only one of them can be declared public.

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Q650. What are the different ways in which dependency injection can be done using Spring Framework ?

Ans. Using Constructor and Setters.

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Q651. Difference between constructor and setter injection ?

Ans. 1. In Setter Injection, partial injection of dependencies can possible, means if we have 3 dependencies like int, string, long, then its not necessary to inject all values if we use setter injection. If you are not inject it will takes default values for those primitives1. In constructor injection, partial injection of dependencies cannot possible, because for calling constructor we must pass all the arguments right, if not so we may get error

2. Setter Injection will overrides the constructor injection value, provided if we write setter and constructor injection for the same property [i already told regarding this, hope you remember ] But, constructor injection cannot overrides the setter injected values

3. If we have more dependencies for example 15 to 20 are there in our bean class then, in this case setter injection is not recommended as we need to write almost 20 setters right, bean length will increase. In this case, Constructor injection is highly recommended, as we can inject all the dependencies with in 3 to 4 lines [i mean, by calling one constructor]

4. Setter injection makes bean class object as mutable [We can change ] .Constructor injection makes bean class object as immutable [We cannot change ]

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Q652. Difference between ApplicationContext and BeanFactory ?

^{This question is still unanswered. Can you please provide an answer.}

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Q653. What are the types of transaction management supported by Spring ?

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Q654. In Java, would you like to see an explicit destructor?

Ans. Yes , a gc method to explicitly call garbage collection immediately on the object. It will provide better flexibility over application that require optimal usage of memory.

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Q655. Write a Program to find age by birth date ?

Ans. LocalDate today = LocalDate.now();
LocalDate birthday = LocalDate.of(1960, Month.JANUARY, 1);
Period p = Period.between(birthday, today); //Now access the values as below
System.out.println(period.getDays());
System.out.println(period.getMonths());
System.out.println(period.getYears());

Sample Code for LocalDate

Sample Code for Period

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Q656. What is a session bean ?

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Q657. Explain Java 8 concurrency mechanism.

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

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Q658. What does the following initialization mean ?

ArrayList<LinkedList> traversalPaths = new ArrayList<LinkedList>();

What could be the use of such a collection.

Ans. Initialize an ArrayList that will hold LinkedLists i.e every element of the arraylist will be a linked list.

Such collection could be used in algorithms that require first random access and then sequential traversal. For example - Storing traversal paths for a graph wherein we can start from any vertex. Implementing dictionary with each arraylist element holding staring with character and then linked list holding duplicate words.

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Q659. Is it a bad practice to initialize object reference to Null ?

Ans. never initialise local to null,yes it is bad pratice

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Q660. What will be the output of following code and Why ?

int x = 5;
int y = 7;
float f = 5f;
float z = y / x * f;
System.out.println(z);

Ans. 5.0

operation between two ints generate int only. so 7/5 generates 1 and not 1.4. Multiplication between int and float generates float and hence

1 * 5.0 = 5.0

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