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Q1621. What is the difference between Java SE Map and Apache Commons MultiMap ? How can we implement functionality similar to multimap using Java SE map ?

Core Java

Ans. We can have duplicate keys within MultiMap whereas we cannot have duplicate keys within Java Util Map.

We can have a Map with value as a "collection of values" instead of single value to have a similar function as Multimap.

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Q1622. What is the difference between return and break statement ?

Core Java

Ans. return is used within a method to return control out of the method. It may be followed by a value which is returned from the method to calling method immediately preceding the point of call.

break statement is used within a loop to move control out of the loop.

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Q1623. What is the difference between return and continue statement ?

Core Java

Ans. return is used within a method to return control out of the method. It may be followed by a value which is returned from the method to calling method immediately preceding the point of call.

continue statement is used within a loop to start next iteration without executing the remaining statements in the loop.

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Q1624. What will happen in a graph traversal if we don't have a check for cycle

Algorithm

Ans. It will result in never ending loop

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Q1625. Given the list of adjacent nodes, What will be the Depth First path

1 -> 2
1 -> 3
1 -> 6
2 -> 4
3 -> 5

Algorithm

Ans. 1 -> 2 -> 4 -> 3 -> 5 -> 6

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Q1626. Given the list of adjacent nodes, What will be the Breadth First path

1 -> 2
1 -> 3
1 -> 6
2 -> 4
3 -> 5

Algorithm

Ans. 1 -> 2 -> 3 -> 6 -> 4 - > 5

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Q1627. What is the difference between Graph's Breadth first and Depth First algorithm ?

Algorithm

Ans. In Breadth first algorithm, all the adjacent nodes of the starting node is visited first and then the same rule is followed while moving inwards whereas

In Depth first algorithm, all the nodes of a single traversal path are visited first till a cycle or an end is found.

For example , given the following entries of adjacent nodes

1,2
1,3
1,6
2,4
2,5
3,6

The Breadth first path would be

1,2,3,6,4,5

and Depth first path would be

1,2,4,5,3,6

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Q1628. What will be the output upon executing main method

public class Graph {
   private static Multimap<Integer,Integer> adjacentDirectedNodesMap = ArrayListMultimap.create();

   Graph(){
      adjacentDirectedNodesMap.put(1, 2);
      adjacentDirectedNodesMap.put(1, 3);
      adjacentDirectedNodesMap.put(1, 4);
      adjacentDirectedNodesMap.put(3, 5);
      adjacentDirectedNodesMap.put(4, 5);
   }

   public static void main(String[] args){
      ArrayList visited = new ArrayList();

      Integer startNode = 1;

      for(Integer adjacentNodes: adjacentDirectedNodesMap.get(startNode)){
            System.out.println(adjacentNodes);
      }
   }
}

Core Java

Ans. Nothing as we haven't yet created an instance and hence adjacentDirectedNodesMap won't be initialized with any value and hence is empty.

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Q1629. What does the following initialization mean ?

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

What could be the use of such a collection.

Core Java

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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Q1630. Difference between Tree and Graph ?

Data Structures

Ans. Graph contain cycles whereas Trees cannot.

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Q1631. Is String final in Java ?

Core Java

Ans. Strings are immutable in Java and not final.

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Q1632. What is the difference between being final and being immutable ? Are string final or immutable in Java ?

Core Java

Ans. Being final in the sense of objects or object reference means that the reference cannot be reassigned to a different object whereas being immutable means that the object contents cannot be changed.

Strings in Java are immutable.

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Q1633. Explain Java 8 concurrency mechanism.

Core Java

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

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Q1634. Will the following code compile ?

final HashMap hm = new HashMap();
hm.put("Ravi", 221);

Core Java

Ans. Yes, it will compile without error. final in this context means that the reference hm cannot be assigned to a new hash map but didn't restrict from changing the state of collection already held by hm.

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Q1635. What will be the output of following code

class TestMain {
public static void main(String[] args) {
String s1 = "ravi";
String s2 = new String("ravi");
Integer i = 10;
Integer a1 = new Integer("10");
System.out.println(s1 == s1);
System.out.println(i == a1);
}
}

Core Java

Ans. false
false

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Q1636. If Table A has 0 records and Table B has 50 records , how many records will the equi join of Table generate ?

SQL

Ans. 0 records

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Q1637. If Table A has 100 records and Table B has 50 records , how many records will the right join of Table A with Table B generate ?

SQL

Ans. 50 records

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Q1638. If Table A has 100 records and Table B has 50 records , how many records will the left join of Table A with Table B generate ?

SQL

Ans. 100 records

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Q1639. If Table A has 100 records and Table B has 50 records , how many records will the equi join of Table generate ?

SQL

Ans. It depends on the join condition.

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Q1640. What is the difference between access and error log ?

Logging

Ans. We log each access to the application resource within access logs, something like

"GET / HTTP/1.0" 200 113 "-" "Mozilla/5.0 zgrab/0.x" "-"

We log only error / warn messages within error logs, something like

ERROR 123#0: *19 connect() failed

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Q1641. What are the different types of log files you have come across ?

Logging

Ans. error , access , authentication , message , database etc

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Q1642. Write code to find second largest number in an array of integers.

Core Java

Ans. int arr[]={1,3,5,6,4,8,9,2,10};
Arrays.sort();
System.out.println(arr[arr.length-1]);

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Q1643. Explain Inheritance and Polymorphism.

Core Java

Ans. Getting parent class object properties into child class is called Inheritance.

The process of representing one form into multiple forms is called polymorphism.

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Q1644. Design a class diagram for a farm.

Design

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

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Q1645. What is a session bean ?

Java EE

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

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Q1646. Write a Program to find age by birth date ?

Core Java

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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Q1647. How to calculate lcm of two numbers ?

Core Java

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

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Q1648. In Java, would you like to see an explicit destructor?

Core Java

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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Q1649. In Java, what is the closest thing to pointers?

Core Java

Ans. References.

Unlike pointers in C , Java references are strongly typed and we cannot do pointer arithmetics with them.

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Q1650. Why do we pass an array of strings to main method ?

Core Java

Ans. Array of strings in the main method are the list of arguments or parameters which are sent to the application / program.

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