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Q1941. Explain Java 8 concurrency mechanism.

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Q1942. 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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Q1943. Difference between Tree and Graph ?

Data Structures

Ans. Graph contain cycles whereas Trees cannot.

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Q1944. 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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Q1945. 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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Q1946. 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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Q1947. 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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Q1948. 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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Q1949. 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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Q1950. 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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Q1951. 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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Q1952. What is the difference between hasNextInt and nextInt method of scanner class ?

Core Java

Ans. The hasNextInt() is used to check if there are any more elements left and the nextInt() is used to access that element.

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Q1953. Is it a bad practice to initialize object reference to Null ?

Core Java

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

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Q1954. 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);

Core Java

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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Q1955. How do you know if a method is a constructor ?

Core Java

Ans. Is the method name same as class Name - Yes

Does the method have any return type ( even void ) - No

It's a constructor

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Q1956. Is a string an array of characters in Java ?

Core Java

Ans. No, String is a class whose objects are called strings in Java.

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Q1957. Can we synchronize the run() method in Java?

Core Java

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Q1958. What are the worst anti patterns in Java ?

Design

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Q1959. Difference between if and switch ? Can we replace all switch statements with if statements ?

Core Java

Ans. if statement is used to do 2 direction branching whereas switch is used to do multi direction branching in Java.

Yes we can replace all switch statements with nested if statements.

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Q1960. What is nested if ?

Core Java

Ans. if statements nested within another if or else blocks are called nested if statements.

if(condition1) {
if(condition2){
}
}

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Q1961. Write a Program to check if the entered number is a Duck Number ( Number having 0 in it ) ?

Core Java

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Q1962. What will the following code print ?

int x[] = new int[5];
x[0] = 1;
x[1] = 2;

for(int count=0;count<x.length;count++){
System.out.println(x[count]);
}

Core Java

Ans. 1
2
0
0
0

As arrays are not dynamically expanded , we have declared the array for size 10. As we have only initialized only 2 values , it will print rest as their default values.

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Q1963. What will the following code print

int x[] = new int[5];
x[0] = 1;
x[1] = 2;

for(int count=0;count<=x.length;count++){
System.out.println(x[count]);
}

Core Java

Ans. 1
2
0
0
0
ArrayIndexOutOfBoundException: 5

As array index starts with 0 and ends with the index of (size - 1), the index 5 is inaccessible for the array and hence will throw the exception.

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Q1964. How to use spring boot to configure different datasources ?

Spring Boot

Ans. https://github.com/jahe/spring-boot-multiple-datasources

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Q1965. what are different pointer operators used ?

Core Java

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Q1966. What is mutable in Java ?

Core Java

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Q1967. Which java features makes java different from other languages ?

Core Java

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Q1968. Why cant we start an identifier with a number in Java?

Core Java

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Q1969. What is the default data type of Serialized methods?'

Core Java

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Q1970. Do we have a method to reverse a string in String class ?

Core Java

Ans. No but we have it in StringBuilder.

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