1. Which allows the removal of elements from a collection? |
|---|
| 1. Iterator |
| 2. Enumeration |
| 3. Both |
| 4. None |
| Answer: 1 |
2. Which of these is not a interface in the Collections Framework? |
|---|
| 1. Collection |
| 2. Set |
| 3. Group |
| 4. List |
| Answer: 3 |
3. What implementation of Iterator can traverse a collection in both directions? |
|---|
| 1. Iterator |
| 2. ListIterator |
| 3. SetIterator |
| 4. MapIterator |
| Answer: 2 |
4. which Map class must be preferred in multi-threading environment to maintain natural order of keys? |
|---|
| 1. ConcurrentHashMap |
| 2. ConcurrentSkipListMap |
| 3. ConcurrentMap |
| 4. All |
| Answer: 2 |
5. What does Collections.sort internally uses when number of elements are greater than 7? |
|---|
| 1. Insertion sort |
| 2. Merge sort |
| 3. Quick sort |
| 4. None |
| Answer: 2 |
6. An attempt to add null key to a TreeMap will result in: |
|---|
| 1. Compile time Exception |
| 2. Error |
| 3. Runtime - NullPointerException |
| 4. None |
| Answer: 3 |
7. Which of these is synchronized and doesn't allow null elements? |
|---|
| 1. Vector |
| 2. CopyOnWriteArraySet |
| 3. CopyOnWriteArrayList |
| 4. ConcurrentSkipListSet |
| Answer: 4 |
8. Which of these collection class has the ability to grow dynamically? |
|---|
| 1. Array |
| 2. Arrays |
| 3. ArrayList |
| 4. None of These |
| Answer: 3 |
9. nextIndex() and previousIndex() are methods of which interface? |
|---|
| 1. IndexIterator |
| 2. Iterator |
| 3. ListIterator |
| 4. NextPreviousIterator |
| Answer: 3 |
10. Which of these packages contain all the collection classes? |
|---|
| 1. java.lang |
| 2. java.util |
| 3. java.net |
| 4. java.awt |
| Answer: 2 |
11. What is Collection in Java? |
|---|
| 1. A group of objects |
| 2. A group of classes |
| 3. A group of interfaces |
| 4. None of the mentioned |
| Answer: 1 |
12. Which of these methods deletes all the elements from invoking collection? |
|---|
| 1. clear() |
| 2. reset() |
| 3. delete() |
| 4. refresh() |
| Answer: 1 |
13. Which interface provides the capability to store objects using a key-value pair? |
|---|
| 1. Java.util.Map |
| 2. Java.util.Set |
| 3. Java.util.List |
| 4. Java.util.Collection |
| Answer: 1 |
14. Which of these interface handle sequences? |
|---|
| 1. Set |
| 2. List |
| 3. Comparator |
| 4. Collection |
| Answer: 2 |
15. Which of these is static variable defined in Collections? |
|---|
| 1. EMPTY_SET |
| 2. EMPTY_LIST |
| 3. EMPTY_MAP |
| 4. All of the mentioned |
| Answer: 4 |
16. Which of these class is superclass of every class in Java? |
|---|
| 1. String class |
| 2. Object class |
| 3. Abstract class |
| 4. ArrayList class |
| Answer: 2 |
17. The methods defined by Thread class that help to manage thread are? |
|---|
| 1. joined |
| 2. stop |
| 3. getname |
| 4. all of the above |
| Answer: 4 |
18. Which of the following method is used to initialize the instance variable of a class |
|---|
| 1. class |
| 2. public |
| 3. constructor |
| 4. Destructor |
| Answer: 3 |
19. A top level class may have which one of the following access modifiers? |
|---|
| 1. package |
| 2. private |
| 3. protected |
| 4. public |
| Answer: 4 |
20. A subclass is also called as? |
|---|
| 1. inner class |
| 2. nested class |
| 3. derived class |
| 4. hidden class |
| Answer: 3 |
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