Java Multiple Choice Questions & Answers - A Door to Success

All the best for the quiz! - Java Quiz part 4

Q.1 Iterator returned by Hashtable on key, value and entry are?

Fail-fast

Fail-safe

none

Q.2 Iterator returned by ConcurrentHashMap on key, value and entry is?

Fail-fast

Fail-safe

None

Q.3 Iterator returned by LinkedHashMap on key, value and entry is?

Fail-fast

Fail-safe

None

Q.4 Iterator returned by TreeMap on key, value and entry is?

Fail-fast

Fail-safe

None

Q.5 Iterator returned by ConcurrentSkipListMap on key, value and entry is?

Fail-fast

Fail-safe

None

Q.6 Which Set implementation is sorted and synchronized?

LinkedHashSet

ConcurrentSkipListSet

TreeSet

CopyOnWriteArraySet

Q.7 TreeMap -
a. Doesn't enable null key
b. Allow several null values

Only a

Only b

Both a and b

Q.8 What will be the output of the following code –

{11=a}

{11=a, 12=b}

UnsupportedOperationException

Compile time exception

Q.9 What will be the output of the following code -

Runtime Exception

Compile time exception

2
{11=bmw, null=fer}

Q.10 What will be the output of the following code -

3
null

2
null

1
null

0
null

Q.11 What will be the output of the following code -

1
null

2
emp1 OVERRIDDEN

3
null

1
emp1 OVERRIDDEN

Q.12 What will be the output of the following code -

1
emp1 OVERRIDDEN

2
emp1 OVERRIDDEN

1
null

3
null

Q.13 What will be the output of the following code -

1
true
1
[1, 3, 4]

3
true
1
[1, 3, 4]

3
false
1
[1, 3, 4]

1
false
1
[1, 2, 4]

Q.14 Which Map is synchronized?
a. Hashtable
b. ConcurrentSkipListMap
c. ConcurrentHashMap

a

b

c

All of these

Q.15 concurrentSkipListMap permits
a. One null key
b. Many null values

Only a

Only b

Both a and b

None

Q.16 What should we use get operations are more?

ArrayList

LinkedList

Any

Q.17 Complexity of ArrayList get method

O(n-1)

O(n)

O(1)

O(2n)

Q.18 Which is sorted by natural order?

LinkedHashSet

TreeSet

HashSet

None

Q.19 Which of these maintains insertion order?
a. List
b. Set

Only a

Only b

Both a and b

Q.20 Which maintains insertion order?

TreeSet

HashSet

LinkedHashSet

None

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Java Multiple Choice Questions & Answers – A Door to Success

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