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Welcome to the java util MCQs Page

Dive deep into the fascinating world of java util with our comprehensive set of Multiple-Choice Questions (MCQs). This page is dedicated to exploring the fundamental concepts and intricacies of java util, a crucial aspect of Java Programming. In this section, you will encounter a diverse range of MCQs that cover various aspects of java util, from the basic principles to advanced topics. Each question is thoughtfully crafted to challenge your knowledge and deepen your understanding of this critical subcategory within Java Programming.

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Check out the MCQs below to embark on an enriching journey through java util. Test your knowledge, expand your horizons, and solidify your grasp on this vital area of Java Programming.

Note: Each MCQ comes with multiple answer choices. Select the most appropriate option and test your understanding of java util. You can click on an option to test your knowledge before viewing the solution for a MCQ. Happy learning!

java util MCQs | Page 2 of 18

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Q11.
What is the premise of equality for IdentityHashMap?

a.

Reference equality

b.

Name equality

c.

Hashcode equality

d.

Length equality

Discuss
Answer: (a).Reference equality
Q12.
What happens if we put a key object in a HashMap which exists?

a.

The new object replaces the older object

b.

The new object is discarded

c.

The old object is removed from the map

d.

It throws an exception as the key already exists in the map

Discuss
Answer: (a).The new object replaces the older object
Q13.
While finding the correct location for saving key value pair, how many times the key is hashed?

a.

1

b.

2

c.

3

d.

unlimited till bucket is found

Discuss
Answer: (b).2
Q14.
Is hashmap an ordered collection.

a.

True

b.

False

c.

May be

d.

Can't say

Discuss
Answer: (b).False
Q15.
If two threads access the same hashmap at the same time, what would happen?

a.

ConcurrentModificationException

b.

NullPointerException

c.

ClassNotFoundException

d.

RuntimeException

Discuss
Answer: (a).ConcurrentModificationException
Q16.
How to externally synchronize hashmap?

a.

HashMap.synchronize(HashMap a);

b.

HashMap a = new HashMap();
a.synchronize();

c.

Collections.synchronizedMap(new HashMap<String, String>());

d.

Collections.synchronize(new HashMap<String, String>());

Discuss
Answer: (c).Collections.synchronizedMap(new HashMap<String, String>());
Q17.
What is the output of below snippet? 
public class Demo
{
  public static void main(String[] args)
  {
  Map<Integer, Object> sampleMap = new TreeMap<Integer, Object>();
  sampleMap.put(1, null); 
  sampleMap.put(5, null); 
  sampleMap.put(3, null); 
  sampleMap.put(2, null); 
  sampleMap.put(4, null); 
 
       System.out.println(sampleMap);
   }
}

a.

{1=null, 2=null, 3=null, 4=null, 5=null}

b.

{5=null}

c.

Exception is thrown

d.

{1=null, 5=null, 3=null, 2=null, 4=null}

Discuss
Answer: (a).{1=null, 2=null, 3=null, 4=null, 5=null}
Q18.
If large number of items are stored in hash bucket, what happens to the internal structure?

a.

The bucket will switch from LinkedList to BalancedTree

b.

The bucket will increase its size by a factor of load size defined

c.

The LinkedList will be replaced by another hashmap

d.

Any further addition throws Overflow exception

Discuss
Answer: (a).The bucket will switch from LinkedList to BalancedTree
Q19.
How can we remove an object from ArrayList?

a.

remove() method

b.

using Iterator

c.

remove() method and using Iterator

d.

delete() method

Discuss
Answer: (c).remove() method and using Iterator
Q20.
How to remove duplicates from List?

a.

HashSet<String> listToSet = new HashSet<String>(duplicateList);

b.

HashSet<String> listToSet = duplicateList.toSet();

c.

HashSet<String> listToSet = Collections.convertToSet(duplicateList);

d.

HashSet<String> listToSet = duplicateList.getSet();

Discuss
Answer: (a).HashSet<String> listToSet = new HashSet<String>(duplicateList);
Page 2 of 18

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