Core Java - Interview Questions and Answers for 'List' | Search Interview Question

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Q41. What are the ways to get the values from list ?

Data Structure

Ans. list.get(index);

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Q42. When do you use a Vector?

Core Java

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Q43. Can we modify a list while iterating it ?

Core Java

Ans. No,we cannot.I t will give concurrentModificationExceptin error. It can be resolved by using ConcurrentClasses like ConcurrentHashMap,CopyOnWriteArrayList,BlockingQueue etc which are fail-safe and wont give exception.

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Q44. Which of the following - arrays or LinkedList allow elements to be accessed using index and how ?

Data Structure

Ans. Arrays allows elements to be accessed directly using the index.

As Array elements are stored in continuous memory locations it's very easy to find the memory address of any element using the formula as following

Memory Address of Array start or index 0 + ( Size of array element * Index )

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Q45. Write code to see if a Linked List has cycle in it ?

or

Write code using Floyd Algorithm to see if a linked list has cycle in it ? What is it's comlexity ?

Algorithm

Ans. public class LinkedList {

Node start = null;
Node head = null;

class Node {
Integer body;
Node nextNode;

Node(Integer value) {
body = value;
}
}

public static void main(String[] args) {
LinkedList ll = new LinkedList();

ll.addNodeToEnd(5);
ll.addNodeToEnd(10);
ll.addNodeToEnd(15);

ll.traverse();

if(checkIfLoop(l1)){
System.out.println("There is a Loop");
} else {
System.out.println("No Loop");
}
}

private boolean checkifLoop(Test l1) {
Node slow = start;
Node fast = start;
Node faster = start;

while(slow != null ) {
fast = slow.nextNode;
faster = fast.nextNode;
if(slow == fast || slow == faster) {
return true;
}
slow = slow.nextNode;
}

return false;
}

}

Complexity of this algorithm is O(n)

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Q46. What can we do if we need to retrieve Fibonacci value at a particular index faster ? Can we use Linked List ?

Data Structure

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Q47. Difference between Arrays and LinkedList ?

Data Structure

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Q48. Detect a loop in a linked list

Data Structure

Ans. Work with two pointers on the linked list - a slow pointer (increments by one node) and a fast pointer (increments by two nodes). If both of these pointers meet at the same node, then there is a cycle in the linked list. Otherwise, no cycle.

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Q49. Difference between List and ArrayList ?

Core Java

Ans. List is an interface whereas ArrayList is an implementation of List.

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Q50. What is the default size of list ? How it is growable ?

Core Java

Ans. Default size is 10.
Regard how size will increase.

Inside add() method there is one method called ensureCapacity() which will check list has enough size available.

This ensureCapacity() method if found size of list need to increase then it will call grow() method which will create new list of extra size and copy existing list data to new one and return.

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Q51. difference between ArrayList and array ?

Core Java

Ans. ArrayList is a variable length collection class whereas arrays are fixed length primitive structure.

We can use generics with arraylist but not with arrays.

We can store primitive data types within arrays but can't with ArrayList. In ArrayList that needs to be converted to Wrapper objects.

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Q52. Difference between ArrayList and HashSet ?

Core Java

Ans. ArrayList is a list , i.e an implementation of List interface whereas HashSet is a Set and an implementation of Set interface.

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Q53. How can we create an arraylist of unique values ?

Core Java

Ans. We can put the value in a set to enforce uniqueness and then dum those value into an arraylist.

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Q54. What is the difference between closing and completing the observer / listener ?

Angular

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Q55. What will be the output of exceuting main method ?

public static void main(String[] args){
      List list = new ArrayList();
      list.add(1);
      list.add(2);
      list.add(3);
      System.out.println(list);
   }

Core Java

a. 1,2,3

b. Order cannot be determined

c. compilation error

d. 3,2,1

Ans.a. 1,2,3

Q56. What will be the output of this code

ArrayList list = new LinkedList();
list.add(3);
list.add(2);
list.add(1);
System.out.println(list);

Core Java

a. 1,2,3

b. 3,2,1

c. Order cannot be determined

d. Compilation Error

Ans.d. Compilation Error

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