Is this true or false. map interface is derived from the collection interface.

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Here you can find objective type Java Programming Objects and Collections questions and answers for interview and entrance examination. Multiple choice and true or false type questions are also provided.

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You can easily solve all kind of Java Programming questions based on Objects and Collections by practicing the objective type exercises given below, also get shortcut methods to solve Java Programming Objects and Collections problems.

Exercise :: Objects and Collections - General Questions

1. 

Suppose that you would like to create an instance of a new Map that has an iteration order that is the same as the iteration order of an existing instance of a Map. Which concrete implementation of the Map interface should be used for the new instance?

A.TreeMapB.HashMapC.LinkedHashMapD.The answer depends on the implementation of the existing instance.

Answer: Option C

Explanation:

The iteration order of a Collection is the order in which an iterator moves through the elements of the Collection. The iteration order of a LinkedHashMap is determined by the order in which elements are inserted.

When a new LinkedHashMap is created by passing a reference to an existing Collection to the constructor of a LinkedHashMap the Collection.addAll method will ultimately be invoked.

The addAll method uses an iterator to the existing Collection to iterate through the elements of the existing Collection and add each to the instance of the new LinkedHashMap.

Since the iteration order of the LinkedHashMap is determined by the order of insertion, the iteration order of the new LinkedHashMap must be the same as the interation order of the old Collection.

---

2. 

Which class does not override the equals() and hashCode() methods, inheriting them directly from class Object?

A.java.lang.StringB.java.lang.DoubleC.java.lang.StringBufferD.java.lang.Character

Answer: Option C

Explanation:

java.lang.StringBuffer is the only class in the list that uses the default methods provided by class Object.

Collection Quiz in Java - MCQ - 150 Multiple choice questions in 6 sets

This Quiz consists of Collection's 150 Multiple choice questions in 6 sets - Java Collection quiz - MCQ
Contents of page >

Note : Each set consists of 25 questions
Each set consists of 5 EASY level difficulty questions 1 mark each.         1 * 5 = 5 marks
Each set consists of 10 MEDIUM level difficulty questions 2 mark each. 2 * 10 = 20 marks
Each set consists of 10 HARD level difficulty questions 3 mark each.       3 * 10 = 30 marks
So, each Set is TOTAL of 55 marks

This quiz have been designed to check beginners and experienced Java developers skills.
Scoring below 15 marks means POOR : You are Java Beginner and need to work very hard.
Scoring 15-34 marks means AVERAGE : You know Java basics, but you need more practice.
Scoring 35-50 marks means GOOD : You have good Java knowledge.
Scoring above 50 marks means EXCELLENT : You have outstanding java knowledge.

Collection Java - MCQ set 1 (25 questions, 55 marks)

Q1 - Q5, 5 EASY level difficulty questions 1 mark each. 1 * 5 = 5 marks


1. Which of these is not a interface in the Collections Framework?

a.Collection
b.Group
c.Set
d.List


2. Which interface restricts duplicate elements?

a.Set
b.List
c.Map
d.(All of these)


3. Which of these collection class has the ability to grow dynamically?

a.Array
b.Arrays
c.ArrayList
d.(None of these)


4. The accuracy and efficiency of a HashMap can be guaranteed with:

a.override equals method
b.override hashCode method
c.(None of these)
d.(All of these)


5. A HashMap allows the existence of:

a.null values
b.one null key
c.(None of these)
d.(All of these)



Q6 - Q15, 10 MEDIUM level difficulty questions 2 mark each. 2 * 10 = 20 marks


6. What implementation of Iterator can traverse a collection in both directions?

a.Iterator
b.ListIterator
c.SetIterator
d.MapIterator


7. The Comparable interface contains which called?

a.toCompare
b.compare
c.compareTo
d.compareWith


8. Which is faster and uses less memory?

a.ListEnumeration
b.Iterator
c.Enumeration
d.ListIterator


9. What Iterator can throw a ConcurrentModificationException?

a.Fail-fast Iterators
b.Fail-safe Iterators
c.(All of these)
d.(None of these)


10. What is the default number of Partitions/segments in Concurrent Hash Map?

a.12
b.32
c.4
d.16


11. Which is best suited to a multi-threaded environment?

a.WeakHashMap
b.Hashtable
c.HashMap
d.ConcurrentHashMap


12. The default capacity of a Vector is:

a.10
b.12
c.8
d.16


13. Which does NOT implement the Collection interface?

a.List
b.Map
c.Set
d.(None of these)


14. The default capacity of a ArrayList is:

a.12
b.16
c.1
d.10


15. Which provides better performance for the insertion and removal from the middle of the list?

a.Vector
b.ArrayList
c.LinkedList
d.(All of these)



Q16 - Q25, 10 HARD level difficulty questions 3 mark each.       3 * 10 = 30 marks


16. What will be output of given code -
    
    
    

a.compile time exception
b.3 2 1
c.1 2 3
d.2 3 1


17. What will be output of given code -
    
    
    

a.1 2 3
b.1 followed by exception
c.Compile time exception
d.Runtime Exception - ClassCastException


18. What will be output of given code -
    
    
    

a.a
    followed by ConcurrentModificationException
b.a b c
c.a b
d.a c


19. An unordered array has a search time complexity of:

a.O(log n)
b.O(n)
c.O(n + 1)
d.O(1)


20. The add and remove methods of TreeSet have a time complexity of:

a.O(n)
b.O(n + 1)
c.O(1)
d.O(log n)


21. After resizing, size of ArrayList is increased by :

a.200%
b.50%
c.100%
d.(None of these)


22. After resizing, size of Vector is increased by:

a.200%
b.100%
c.50%
d.(None of these)


23. What will be output of given code -
    
    
    

a.will execute without any exception
b.(None of these)
c.compilation error
d.Throw ConcurrentModificationException


24. Deque and Queue are derived from:

a.AbstractList
b.Collection
c.AbstractCollection
d.List


25. What will be output of given code -
    
    
    

a.[name=ankit, name=brad]
b.[name=brad, name=ankit]
c.Runtime Exception
d.compile time exception

Quiz 1 - Correct answers

EASY
1) b
2) a
3) c
4) d
5) d

MEDIUM
6) b
7) c
8) c
9) a
10) d
11) d
12) a
13) b
14) d
15) c

HARD
16) b
17) d
18) a
19) b
20) d
21) b
22) b
23) d
24) b
25) a

Collection Java - MCQ set 2 (25 questions, 55 marks)

Q1 - Q5, 5 EASY level difficulty questions 1 mark each. 1 * 5 = 5 marks


1. What guarantees type-safety in a collection?

a.Generics
b.Abstract classes
c.Interfaces
d.Collection


2. HashSet internally uses?

a.Set
b.HashMap
c.List
d.Collection


3. The most used interfaces from the Collection framework are?

a.List
b.Map
c.Set
d.(All of these)


4. The root interface of Java Collection framework hierarchy is -

a.Collection
b.Root
c.Collections
d.List/Set


5. Which of these is synchronized?

a.ArrayList
b.LinkedList
c.Vector
d.(None of these)



Q6 - Q15, 10 MEDIUM level difficulty questions 2 mark each. 2 * 10 = 20 marks


6. ArrayList implements which of the following?

a.List
b.RandomAccess
c.Cloneable
d.(All of these)


7. Which of these allows the storage of many null values?

a.Set
b.List
c.(None of these)
d.(All of these)


8. nextIndex() and previousIndex() are methods of which interface?

a.IndexIterator
b.Iterator
c.ListIterator
d.NextPreviousIterator


9. Vector extends which of these?

a.ArrayList
b.LinkedList
c.AbstractList
d.None


10. LinkedList implements?

a.Deque
b.List
c.None
d.All


11. In Iterator, nextElement() method of Enumeration has been changed to:

a.next()
b.getNext()
c.returnNext()
d.name remains same


12. Enumeration returned by Vector is?

a.fail-fast
b.fail-safe
c.none

13. From Java 5 onwards, which one of these is recommended to replace Hashtable?

a.ConcurrentHashMap
b.HashMap
c.ConcurrentHashtable
d.None


14. Which does not allow to store a null value?

a.TreeSet
b.LinkedHashSet
c.HashSet
d.None


15. Iterator returned by Vector is?

a.fail-fast
b.fail-safe
c.none



Q16 - Q25, 10 HARD level difficulty questions 3 mark each.       3 * 10 = 30 marks


16. What describes how well an algorithm performs in best, average or worse case scenarios?

a.Big-B
b.Big-O
c.Big-Data
d.Big-N


17. An ordered array has a search time complexity of?

a.O(n)
b.O(1)
c.O(log n)
d.O(n-1)


18. Which Map class must be preferred in multi-threading environment to maintain natural order of keys?

a.ConcurrentHashMap
b.ConcurrentSkipListMap
c.ConcurrentMap
d.all


19. What will be output of following code -
    
    
    

a.[null, 1]
b.[1]
c.[null, 1, 1, null]
d.Runtime Exception


20. What will be output of following code -
    
    
    

a.{a=ferrari}
b.{a=audi, a=ferrari}
c.{a=audi}
d.null


21. What will be output of following code -
    
    
    

a.{a=ferrari}
b.{a=audi, a=ferrari}
c.Runtime Exception
d.{a=audi}


22. TreeMap implements?

a.Dictionary
b.HashMap
c.AbstractMap
d.NavigableMap


23. Which list class must be preferred in multi-threading environment, considering performance constraint

a.Vector
b.CopyOnWriteArrayList
c.ArrayList
d.ConcurrentArrayList


24. Which Set class must be preferred in multi-threading environment, considering performance constraint

a.HashSet
b.ConcurrentSkipListSet
c.LinkedHashSet
d.CopyOnWriteArraySet


25. Which Map class must be preferred in multi-threading environment, considering performance constraint

a.Hashtable
b.CopyOnWriteMap
c.ConcurrentHashMap
d.ConcurrentMap

Quiz 2 - Correct answers

EASY
1) a
2) b
3) d
4) a
5) c

MEDIUM
6) d
7) b
8) c
9) c
10) d
11) a
12) b
13) a
14) a
15) a

HARD
16) b
17) c
18) b
19) c
20) a
21) b
22) d
23) b
24) b
25) c

Collection Java - MCQ set 3 (25 questions, 55 marks)

Q1 - Q5, 5 EASY level difficulty questions 1 mark each. 1 * 5 = 5 marks


1. Which allows the removal of elements from a collection?

a.Enumeration
b.Iterator
c.Both
d.None


2. The Comparator interface contains the method?

a.compareWith()
b.compareTo()
c.compare()
d.


3. Which of these is synchronized?

a.TreeMap
b.HashMap
c.Hashtable
d.All


4. Which is more offers best performance?

a.TreeMap
b.HashMap
c.LinkedHashMap
d.All are equal


5. Which of these class should be preferred to be used as a key in a HashMap?

a.String
b.Integer
c.Double
d.Any of these



Q6 - Q15, 10 MEDIUM level difficulty questions 2 mark each. 2 * 10 = 20 marks


6. What should we use when add and remove operations are more frequent than get operations?

a.LinkedList
b.ArrayList
c.Vector
d.All


7. Iterator returned by ArrayList is?

a.Fail-fast
b.Fail-safe
c.none


8. Iterator returned by LinkedList is?

a.Fail-fast
b.Fail-safe
c.none


9. Iterator returned by CopyOnWriteArrayList is ?

a.Fail-fast
b.Fail-safe
c.none


10. Iterator returned by HashMap on key, value and entry is?

a.Fail-fast
b.Fail-safe
c.none


11. Iterator returned by Hashtable on key, value and entry is?

a.Fail-fast
b.Fail-safe
c.none


12. Iterator returned by ConcurrentHashMap on key, value and entry is?

a.Fail-fast
b.Fail-safe
c.none


13. Iterator returned by LinkedHashMap on key, value and entry is?

a.Fail-fast
b.Fail-safe
c.none


14. Iterator returned by TreeMap on key, value and entry is?

a.Fail-fast
b.Fail-safe
c.none


15. Iterator returned by ConcurrentSkipListMap on key, value and entry is?

a.Fail-fast
b.Fail-safe
c.none



Q16 - Q25, 10 HARD level difficulty questions 3 mark each.       3 * 10 = 30 marks


16. Which Set implementation is sorted and synchronized?

a.LinkedHashSet
b.ConcurrentSkipListSet
c.TreeSet
d.CopyOnWriteArraySet


17. TreeMap -

a.doesn't allow null key
b.allow many null values
c.All
d.None


18. What will be output of following code -
    
    
    

a.{11=a}
b.{11=a, 12=b}
c.UnsupportedOperationException
d.Compile time exception


19. What will be output of following code -
    
    
    

a.Runtime Exception
b.Compile time exception
c.{11=a, null=c}
d.{11=a, null=null}


20. What will be output of following code -
    
    
    

a.3
        null
b.2
        null
c.1
        null
d.0
        null


21. What will be output of following code -
    
    
    

a.1
        null
b.2
        emp1 OVERRIDDEN
c.3
        null
d.1
        emp1 OVERRIDDEN


22. What will be output of following code -
    
    
    

a.1
        emp1 OVERRIDDEN
b.2
        emp1 OVERRIDDEN
c.1
        null
d.3
        null


23. What will be output of following code -
    
    
    

a.1
       true
       1
       [1, 3, 4]
b.3
       true
       1
       [1, 3, 4]
c.3
       false
       1
       [1, 3, 4]
d.1
       false
       1
       [1, 2, 4]


24. Which Map is synchronized?

a.Hashtable
b.ConcurrentSkipListMap
c.ConcurrentHashMap
d.All


25. concurrentSkipListMap allows

a.one null key
b.many null values
c.all
d.none

Quiz 3 - Correct answers

EASY
1) b
2) c
3) c
4) b
5) d

MEDIUM
6) a
7) a
8) a
9) b
10) a
11) a
12) b
13) a
14) a
15) b

HARD
16) b
17) c
18) b
19) a
20) a
21) c
22) d
23) a
24) d
25) d

Collection Java - MCQ set 4 (25 questions, 55 marks)

Q1 - Q5, 5 EASY level difficulty questions 1 mark each. 1 * 5 = 5 marks


1. What should we use get operations are more?

a.ArrayList
b.LinkedList
c.Any


2. Complexity of ArrayList get method

a.O(n-1)
b.O(n)
c.O(1)
d.O(2n)


3. Which is sorted by natural order?

a.LinkedHashSet
b.TreeSet
c.HashSet
d.None


4. Which of these maintains insertion order?

a.List
b.Set
c.All
d.None


5. Which maintains insertion order?

a.TreeSet
b.HashSet
c.LinkedHashSet
d.None



Q6 - Q15, 10 MEDIUM level difficulty questions 2 mark each. 2 * 10 = 20 marks


6. In Iterator, hasMoreElements() method of Enumeration has been changed to:

a.hasNextElement()
b.isNext()
c.hasNext()
d.name remains same


7. TreeSet internally uses which one to store elements?

a.HashMap
b.LinkedHashMap
c.TreeMap
d.None


8. HashSet internally uses?

a.HashMap
b.LinkedHashMap
c.TreeMap
d.None


9. An attempt to add null key to a TreeSet will result in:

a.Will compile
b.Compile time Exception
c.Error
d.Runtime - NullPointerException


10. What is initial capacity of LinkedList?

a.8
b.10
c.16
d.10


11. Enumeration returned by ArrayList is

a.Fail-fast
b.Fail-safe
c.none


12. LinkedHashMap allows

a.one null key
b.many null values
c.none
d.all


13. Hashtable allows

a.one null key
b.many null values
c.none
d.all


14. How can you sort given HashMap on basis of values

a.Implement Comparator interface and override its compare method
b.It's not possible
c.Implement Comparator interface and override its compareTo method
d.Implement Comparator and Comparable interface


15. What will be output of following code -
    
    
    

a.1
        null
b.2
        emp1 OVERRIDDEN
c.2
        null
d.1
        emp1 OVERRIDDEN



Q16 - Q25, 10 HARD level difficulty questions 3 mark each.       3 * 10 = 30 marks


16. What does Collections.sort internally uses when number of elements are less than 7?

a.Insertion sort
b.Merge sort
c.Quick sort
d.None


17. What does Collections.sort internally uses when number of elements are greater than 7?

a.Insertion sort
b.Merge sort
c.Quick sort
d.None


18. An attempt to add null key to a TreeMap will result in:

a.Compile time Exception
b.Error
c.Runtime - NullPointerException
d.None


19. What will be output of following code -
    
    
    

a.Compile time exception
b.1
        {null=null}
c.2
        {11=bmw, null=fer}
d.Runtime Exception

20. Which of these is synchronized and doesn't allow null elements?

a.Vector
b.CopyOnWriteArraySet
c.CopyOnWriteArrayList
d.ConcurrentSkipListSet


21. Which of these is synchronized and isn't sorted by natural order?

a.EnumSet
b.LinkedList
c.ConcurrentSkipListSet
d.Vector


22. What will be output of following code -
    
    
    

a.11 followed by ConcurrentModificationException
b.11
c.ConcurrentModificationException
d.Compile time exception


23. What will be output of following code -
    
    
    

a.ind followed by NullPointerException
b.ind followed by ConcurrentModificationException
c.ind usa null
d.ind usa followed by NullPointerException


24. What will be output of following code -
    
    
    

a.daysEnumMap.get(Days.Monday) : Day1
        daysEnumMap.containsKey(Days.Monday) : true
b.daysEnumMap.get(Days.Monday) : Day1
        daysEnumMap.containsKey(Days.Monday) : false
c.Runtime Exception
d.Compile time exception


25. In ListIterator, after a call to next() or previous(), if a call is made to set(E element) followed by add() or remove() what happens?

a.compilation error
b.UnsupportedOperationException
c.ConcurrentModificationException
d.none

Quiz 4 - Correct answers

EASY
1) a
2) c
3) b
4) a
5) c

MEDIUM
6) c
7) c
8) a
9) d
10) b
11) a
12) d
13) c
14) a
15) b

HARD
16) a
17) b
18) c
19) c
20) d
21) d
22) b
23) c
24) d
25) b

Collection Java - MCQ set 5 (25 questions, 55 marks)

Q1 - Q5, 5 EASY level difficulty questions 1 mark each. 1 * 5 = 5 marks


1. Which interface must be implemented for sorting on basis many criterias

a.Comparator
b.Comparable
c.Serializable
d.None


2. Can 2 threads on same ConcurrentHashMap object access it concurrently

a.we need to add additional functionality to achieve the same.
b.Its not possible
c.different threads can access different segments concurrently.


3. What will be output of following code -
   
   
   

a.Listl=new ArrayList();
b.Listl=new ArrayList();
c.Listl=new ArrayList();
d.Listl=new ArrayList();


4. Which of these provides a get(in index) method?

a.Map
b.Set
c.List
d.All


5. LinkedHashSet implements:

a.Set
b.Cloneable
c.Serializable
d.All



Q6 - Q15, 10 MEDIUM level difficulty questions 2 mark each. 2 * 10 = 20 marks


6. What will be output of following code -
   
   
   

a.a
        b
        c
        followed by Exception
b.Runtime Exception
c.Compile time exception
d.a
        b


7. In WeakHashMap

a.An entry are automatically removed by garbage collector
b.Behaves normally like HashMap
c.An entry are never removed by garbage collector
d.None


8. A EnumSet

a.Can use enum and non enum type keys
b.Cannot use enum type keys
c.is specialized Set implementation for use with enum type keys only
d.None


9. Iterator returned by HashSet is

a.Fail-fast
b.Fail-safe
c.none


10. Iterator returned by CopyOnWriteArraySet is

a.Fail-fast
b.Fail-safe
c.none


11. Iterator returned by TreeSet is

a.Fail-fast
b.Fail-safe
c.none


12. Iterator returned by LinkedHashSet is

a.Fail-fast
b.Fail-safe
c.none


13. Iterator returned by ConcurrentSkipListSet is

a.Fail-fast
b.Fail-safe
c.none


14. Which List is synchronized?

a.Vector
b.CopyOnWriteArrayList
c.All
d.none


15. Which Set is synchronized?

a.CopyOnWriteArraySet
b.ConcurrentSkipListSet
c.All
d.none



Q16 - Q25, 10 HARD level difficulty questions 3 mark each.       3 * 10 = 30 marks


16. What will be output of following code -
    
    
    

a.a
        b
        a
        b
b.a
        b
c.will print a infinite times
d.a


17. What is significance of using instanceOf operator and getClass() in equals method

a.instanceOf will return true for comparing current class with its subclass as well
b.getClass() will return true only if exactly same class is compared
c.getClass() will return false when compared with subclass
d.All


18. What will be output of following code -
    
    
    

a.11 44
b.Runtime Exception
c.Compile time exception
d.44 11


19. What will be output of following code -
    
    
    

a.0
        null
b.1
        null
c.2
        null
d.3
        null


20. What will be output of following code -
    
    
    

a.Compile time exception
b.a b c d e 1
c.a b c d e 2
d.e d c b a -1


21. What will be output of following code -
    
    
    

a.5
        is WeekDay
        is weekEnd
        true
        0
b.2
        is WeekDay
        is weekEnd
        true
        0
c.2
        is WeekEnd
        is weekDay
        true
        0
d.Compile time exception


22. What will be output of following code -
    
    
    

a.[1, 1, 2, 3]
b.[1, 2, 2, 3]
c.[1, 1, 3, 2]
d.[1, 2, 3]


23. What will be output of following code -
    
    
    

a.[{name=amy, id=2}, {name=sam, id=4}]
b.Runtime Exception
c.compile time exception
d.[{name=sam, id=4}, {name=amy, id=2}]


24. What will be output of following code -
    
    
    

a.[2, 3]
b.Runtime Exception
c.compile time exception
d.None


25. What will be output of following code -
    
    
    

a.3
b.3.0
c.compile time exception
d.runtime exception

Quiz 5 - Correct answers

EASY
1) a
2) c
3) d
4) c
5) d

MEDIUM
6) d
7) a
8) c
9) a
10) b
11) a
12) a
13) b
14) c
15) c

HARD
16) c
17) d
18) b
19) d
20) d
21) a
22) c
23) d
24) c
25) c

Collection Java - MCQ set 6 (25 questions, 55 marks)

Q1 - Q5, 5 EASY level difficulty questions 1 mark each. 1 * 5 = 5 marks


1. Which of these does NOT have an index based structure?

a.List
b.Set
c.Map
d.


2. java.util.Collections is a:

a.class
b.interface
c.object
d.none


3. Methods such as reverse, shuffle and sort are available in:

a.Object
b.Collection
c.Collections
d.Apache Commons Collections


4. Which of these allows duplicate elements?

a.Set
b.List
c.All
d.None


5. Which allows the storage of a null key and many null values?

a.Hashtable
b.HashMap
c.Both
d.None



Q6 - Q15, 10 MEDIUM level difficulty questions 2 mark each. 2 * 10 = 20 marks


6. What will be output of following code -
   
   
   

a.1
        {null=null}
b.2
        {null=null, 11=a}
c.Runtime Exception
d.Compile time exception


7. What will be output of following code -
   
   
   

a.1
        2
b.1
        2
        3
c.3
        2
        1
d.ConcurrentModificationException


8. What will be output of following code -
   
   
   

a.Listl=new ArrayList>();
b.List> l=new ArrayList>();
c.Listl=new ArrayList();
d.List> l=new ArrayList>();


9. What will be output of following code -
   
   
   

a.[a, d, b, c]
b.[a, b, c, d]
c.[d, a, d, c]
d.none


10. What will be output of following code -
    
    
    

a.1
b.2
c.0
d.4


11. What will be output of following code -
    
    
    

a.{11=audi, null=null}
b.{null=null}
c.{11=bmw, null=fer}
d.Runtime Exception


12. What will be output of following code -
    
    
    

a.[]
b.[{name=sam, id=4}, {name=amy, id=2}]
c.[{name=amy, id=2}, {name=sam, id=4}]
d.[null]


13. What will be output of following code -
    
    
    

a.1 2 1.1 2.2
b.Runtime Exception
c.compile time exception
d.None


14. What will be output of following code -
    
    
    

a.5.0
b.5
c.Runtime Exception
d.compile time exception


15. What will be output of following code -
    
    
    

a.3
        null
b.1
        emp1 OVERRIDDEN
c.2
        emp1 OVERRIDDEN
d.3
        emp1 OVERRIDDEN



Q16 - Q25, 10 HARD level difficulty questions 3 mark each.       3 * 10 = 30 marks


16. What will be output of following code -
    
    
    

a.[3, 2, 1]
b.compile time exception
c.Runtime Exception
d.[1, 2, 3]


17. What will be output of following code -
    
    
    

a.[1, 2, 3]
b.Runtime Exception - classCastException
c.[3, 2, 1]
d.None


18. What will be output of following code -
    
    
    

a.[3, 2, 1]
b.Runtime Exception - NullPointerException
c.[1, 2, 3]
d.Runtime Exception - classCastException


19. What will be output of following code -
    
    
    

a.{4=1, 3=1, 2=1}
b.{2=1, 3=1, 4=1}
c.{4=1, 2=1, 3=1}
d.compile time exception


20. What will be output of following code -
    
    
    

a.Runtime Exception
b.412
c.124
d.421


21. What will be output of following code -
    
    
    

a.542
b.245
c.425
d.None


22. What will be output of following code -
    
    
    

a.Runtime Exception - NullPointer
b.Runtime Exception - IndexOutOfBound
c.compile time error
d.23


23. What will be output of following code -
    
    
    

a.IndexOutOfBoundException
b.23
c.compile time error
d.NullPointerException


24. In ConcurrentHashMap - When thread locks one segment for updation it does not block it for retrieval hence some other thread can read the same segment, but it will be able to read the data before locking?

a.true
b.false
c.may be true/false

25. In ConcurrentHashMap - When thread locks one segment for updation it does not allow any other thread to perform updations in same segment until lock is not released on segment

a.true
b.false
c.may be true/false

Quiz 6 - Correct answers

EASY
1) b
2) a
3) c
4) b
5) b

MEDIUM
6) b
7) d
8) d
9) a
10) b
11) d
12) c
13) a
14) a
15) b

HARD
16) b
17) a
18) b
19) a
20) b
21) a
22) d
23) c
24) a
25) a

Labels: Core Java Exam java Java Mcq(Multiple choice questions) Java QUIZ

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