Interview Questions

1. 1.The given program is used to check weather the object is instance of class or not? public class Deccansoft { public static void main(String[] args) { Object o=new ArrayList().iterator(); System.out.println((o instanceof List)+","); System.out.println((o instanceof Iterator)+","); System.out.println(o instanceof ListIterator); } }

Options:

a. false, false, false

b. false, false, true

c. false, true, false

d. false, true, true

Reveal Answer

2. 2. Which of these methods deletes all the elements from invoking?

Options:

a. clear()

b. refresh()

c. reset()

d. delete()

Reveal Answer

3. 3. which of these interface is not a part of java collection framework?

Options:

a. List

b. Set

c. SortedList

d. SortedMap

Reveal Answer

4. 4.Given program is used to adding and removing the elements using vector class. Find the output? class Deccansoft { public static void main(String args[]) { Vector obj = new Vector(4,2); obj.addElement(new Integer(3)); obj.addElement(new Integer(2)); obj.addElement(new Integer(5)); obj.removeAll(obj); System.out.println(obj.isEmpty()); } }

Options:

a. 0

b. 1

c. true

d. false

Reveal Answer

5. 5.Given program is used to adding and deleting elements using Stack. find predicted output? class Deccansoft { public static void main(string args[]) { Stack obj = new Stack(); obj.push(new Integer(8)); obj.push(new Integer(2)); obj.pop(); obj.push(new Integer(5)); System.out.println(obj); } }

Options:

a. [3, 5]

b. [3, 2]

c. [3, 2, 5]

d. [3, 5, 2]

Reveal Answer

6. 6. Given program is used to assigning the values to the using Hashtable. class public static void main(String args[]) { Hashtable obj= new Hashtable(); obj.put(“A”, new Integer(3)); obj.put(“B”, new Integer(2)); obj.put(“C”, new Integer(8)); obj.remove(new String(“A”)); System.out.println(obj); } }

Options:

a. {C=8, B=2}

b. {C=8, B=2}

c. {A=3, C=8, B=2}

d. {A=3, C=8, B=2}

Reveal Answer

7. 7. Given program is used to adding and removing set of Integers using BitSet. Predict the generated output? public class Deccansoft { public static void main(String[] args) { BitSet obj=new BitSet(5); for(int i=0; i<5;++i) obj.set(i); obj.clear(2); System.out.println(obj); } }

Options:

a. {0, 1, 3, 4}

b. {0, 1, 2, 4}

c. {0, 1, 2, 3, 4}

d. {0, 0, 0, 3, 4}

Reveal Answer

8. 8. Find the output for this program? public class Deccansoft { public static void main(String[] args) { BitSet obj=new BitSet(5); for(int i=0; i<5;++i) obj.set(i); obj.clear(2); System.out.println(obj); } }

Options:

a. {0, 1, 3, 4}

b. { }

c. {0, 1, 2, 3, 4}

d. {0, 0, 0, 3, 4}

Reveal Answer

9. 9. Given programs is used to add elements in any order. Find the generated output for it? class Deccansoft { public static void main(String args[]) { ArrayList obj=new ArrayList(); obj.add(“A”); obj.add(“B”); obj.add(“C”); obj(1,”D”); System.out.println(obj); } }

Options:

a. [A, B, C, D]

b. [A, D, B, C]

c. [A, D, C]

d. [A, B, C]

Reveal Answer

10. 10. Given program is used to find the length of the object? class Deccansoft { ArrayList obj=new ArrayList() { obj.add(“A”); obj.add(0,”B”); System.out.print(obj.size()); } }

Options:

a. 0

b. 1

c. 2

d. garbage value

Reveal Answer

11. 11. Find the capacity of the given program? class Deccansoft { ArrayList obj= new ArrayList(); obj.add(“A”); obj.ensureCapacity(3); ob.trimToSize(); System.out.println(obj.size()); } }

Options:

a. 1

b. 2

c. 3

d. 4

Reveal Answer

12. 12. Given program is used to add elements to first. Predict the output for this code? public class AddingElementsFirst { public static void main(String[] args) { LinkedList li=new LinkedList(); li.add("A"); li.add("B"); li.add("C"); li.addFirst("D"); li.addLast("B"); li.clone(); li.descendingIterator(); System.out.println(li); } }

Options:

a. 5 [D, A, B, C, B]

b. [D,A, C, B] 4

c. [D, A, C, B]

d. [D, C, A, B] 3 [D, A, C, B] 8

Reveal Answer

13. 13. Given program is used to add elements using Tree set. Find the generated output? public class Deccansoft { public static void main(String[] args) { TreeSet t= new TreeSet(); t.add("3"); t.add("9"); t.add("A"); t.add("A"); t.add("BCD"); t.descendingSet(); t.comparator(); t.floor(t); System.out.println(t); } }

Options:

a. [3, 9, A, BCD]

b. [3, 9, A, A, BCD]

c. Exception

d. [3, 9, a, BCD]

Reveal Answer

14. 14. Find the output for this code? public class Deccansoft { public static void main(String[] args) { HashMap obj= new HashMap(); obj.put("A", new Integer(1)); obj.put("B", new Integer("hello")); obj.put("C", new Integer(5)); System.out.println(obj); } }

Options:

a. [A=1, B=hello, C=5]

b. [A=1, B=1056452, C=5]

c. Exception

d. compiler error

Reveal Answer

15. 15. Find the output for this code? public class Deccansoft { public static void main(String[] args) { HashMap obj= new HashMap(); obj.put("A", new Integer(1)); obj.put("B", new Integer(2)); obj.put("C", new Integer(3)); obj.remove(obj); System.out.println(obj.keySet()); System.out.println(obj.get("B")); } }

Options:

a. [] 2

b. [A, B, C] 2

c. [] 0

d. Exception

Reveal Answer

16. 16. Find the generated output for this code? public class Deccansoft { public static void main(String[] args) { Vector obj= new Vector(1,5); obj.setSize(1); obj.addElement(new Integer(3)); obj.addElement(new Integer(2)); obj.addElement(new Integer(5)); obj.insertElementAt(8,1); System.out.println(obj); System.out.println(obj.contains(5)); } }

Options:

a. [null, 8, 3, 2, 5] true

b. [8, 3, 2, 5] true

c. Exception

d. [0, 8, 3, 2, 5] true

Reveal Answer

17. 17. Given code is used to push and pop the elements using stack. and find the output? class Deccansoft <E> { Stack<E> st= new Stack<E>(); public void push(E obj) { st.push(obj); } public E pop() { E obj=st.pop(); return obj; } } class Reclaiming { public static void main(String args[]) { Deccansoft<String> gs=new Deccansoft<String>(); gs.push(“Hello”); System.out.println(gs.pop()); } }

Options:

a. H

b. Hello

c. Exception

d. Compiler error

Reveal Answer

18. 18. Choose the output for this code? class Deccansoft<E> { Stack<E> st=new Stack<E>(); public void push(E obj) { st.push(obj); } public E pop() { E obj=st.pop(); return obj; } } class New { public static void main(String args[]) { Deccansoft<Integer> d=new Deccansoft<Integer>(); d.push(36); System.out.print(d.pop()); } }

Options:

a. 0

b. 36

c. compiler error

d. Exception

Reveal Answer

19. 19.Find the output for this code? Class Deccansoft { public static void main(String args[]) { ListIterator a =List.listIterator(); if(a.previousIndex()!=-1) while(a.hasNext()) System.out.println(a.next()+” ”); else System.out.print(“empty”); } }

Options:

a. 0

b. 1

c. -1

d. empty

Reveal Answer

20. 20. Given code is used to find reverse of a number. Find if any errors or generated output in it? class Deccansoft { public static void main(String args[]) { LinkedList list=new LinkedList(); list.add(new Integer(2)); list.add(new Integer(8)); list.add(new Integer(3)); list.add(new Integer(1)); Iterator i=List.iterator(); Collections.reverse(list); while(i.hasnext()+””); } }

Options:

a. 2 8 5 1

b. 1 5 8 2

c. 2

d. 1 2 1 8 5

Reveal Answer

21. 21. Find the output for this code? Class Deccansoft { public static void main(string args[]) { LinkedList list= new LinkedList(); List.add(new Integer(2)); list.add(new Integer(8)); list.add(new Integer(5)); list.add(new Integer(1)); Iterator i=list.iterator(); Collections.reverse(list); i.next(); i.remove(); while(i.hasNext()) System.out.println(i.next()+” “); } }

Options:

a. 2 8 5

b. 2 1 8

c. 2 5 8

d. 8 5 1

Reveal Answer

22. 22. This code is used to accept an array and displaying it. Select the generated output? Class Deccansoft { static<T> void display(T[] arr) { for(T i: arr) System.out.println(i); } } class New { public static void main(String args[]) { Integer arr[]={1, 2, 3, 4, 5, 6}; System.out.println(“reading data”); ArrayList ar=new ArrayList(); ar.set(1, arr); Deccansoft.display(arr); } }

Options:

a. 1 2 3 4 5 6

b. Exception

c. 1 1 1 1 1 1

d. compiler error

Reveal Answer

23. 23. Find the generated output? Class Deccansoft<E> { Stack<E> st=new Stack<E>(); public void push(E obj) { st.push(obj); } public E pop() { E obj=st.pop(); return obj; } } class New { public static void main(String args[]) { Deccansoft] <String> ds=new Deccansoft<String>(); ds.push(“hello”); System.out.print(ds.pop()+” “); Deccansoft <Integer>ds=new Deccansoft<Integer>(); ds.push(36); System.out.print(ds.pop()); } }

Options:

a. error

b. hello

c. 36

d. hello 36

Reveal Answer

24. 24. Collection stores only ?

Options:

a. object type data

b. primitive type data

c. string type data

d. All of the above

Reveal Answer

25. 25.Which type of exception is thrown if you try to add an element to an already full Collection ?

Options:

a. IllegalArgumentException

b. IllegalStateException

c. ClassCastException

d. NullPointerException

Reveal Answer

26. 26. Which interface does NavigableSet implements ?

Options:

a. Set

b. List

c. Collection

d. SortedSet

Reveal Answer

27. 27. What does get(int index) method define by List interface do ?

Options:

a. returns object stored at the specified index

b. store object at the specified index

c. returns a list containing elements between specified index and end in the collection.

d. none of the above.

Reveal Answer

28. 28. Which of the following interface guarantees that no duplicates elements are stored and all elements are accessed in natural order ?

Options:

a. java.util.List

b. java.util.Set

c. java.util.Deque

d. ava.util.Map

Reveal Answer

29. 29. Which of the following statement is not true about ArrayList class ?

Options:

a. ArrayList class extends AbstractList class and implements the List interface

b. ArrayList supports dynamic array that can grow as needed

c. ArrayLists are synchronized.

d. It can coontain Duplicate elements and maintains the insertion order

Reveal Answer

30. 30. Which of the following statement is true about TreeSet class ?

Options:

a. TreeSet extends AbstractList class and implements the List interface.

b. Access and retrieval times are quite slow.

c. TreeSet stores elements sorted ascending order

d. Uses a LinkedList structure to store elements

Reveal Answer

31. 31. Which class does java.util.Properties extends ?

Options:

a. java.util.HashMap

b. java.util.Hashtable

c. java.util.LinkedHashMap

d. java.util.LinkedList

Reveal Answer

32. 32. Which interface is used to traverse a list in both forward and backward direction ?

Options:

a. Iterator interface

b. ListIterator interface

c. Enumeration interface

d. None of the above

Reveal Answer

33. 33. Which interface provides the capability to store objects using a key-value pair ?

Options:

a. java.util.Map

b. java.util.Set

c. java.util.List

d. java.util.Collection

Reveal Answer

34. 34. Which of the following method is used to return a Set that contains the entries in a map ?

Options:

a. keyset()

b. getSet()

c. entrySet()

d. getAll()

Reveal Answer

35. 35. Which of the following statement is not correct about HashMap class ?

Options:

a. HashMap class extends AbstractMap and implements Map interface.

b. HashMap class is not synchronized.

c. HashMap uses a hashtable to store the map.

d. HashMap maintain order of its element.

Reveal Answer

36. 36. Which of the following class provide the facility to specify default value that is used when no value is associated with a certain key ?

Options:

a. java.util.HashMap

b. java.util.Hashtable

c. java.util.Properties

d. java.util.LinkedHashMap

Reveal Answer

Interview Questions and Answer

2. 2. Which of these methods deletes all the elements from invoking?

3. 3. which of these interface is not a part of java collection framework?

5. 5.Given program is used to adding and deleting elements using Stack. find predicted output? class Deccansoft { public static void main(string args[]) { Stack obj = new Stack(); obj.push(new Integer(8)); obj.push(new Integer(2)); obj.pop(); obj.push(new Integer(5)); System.out.println(obj); } }

7. 7. Given program is used to adding and removing set of Integers using BitSet. Predict the generated output? public class Deccansoft { public static void main(String[] args) { BitSet obj=new BitSet(5); for(int i=0; i<5;++i) obj.set(i); obj.clear(2); System.out.println(obj); } }

8. 8. Find the output for this program? public class Deccansoft { public static void main(String[] args) { BitSet obj=new BitSet(5); for(int i=0; i<5;++i) obj.set(i); obj.clear(2); System.out.println(obj); } }

9. 9. Given programs is used to add elements in any order. Find the generated output for it? class Deccansoft { public static void main(String args[]) { ArrayList obj=new ArrayList(); obj.add(“A”); obj.add(“B”); obj.add(“C”); obj(1,”D”); System.out.println(obj); } }

10. 10. Given program is used to find the length of the object? class Deccansoft { ArrayList obj=new ArrayList() { obj.add(“A”); obj.add(0,”B”); System.out.print(obj.size()); } }

11. 11. Find the capacity of the given program? class Deccansoft { ArrayList obj= new ArrayList(); obj.add(“A”); obj.ensureCapacity(3); ob.trimToSize(); System.out.println(obj.size()); } }

14. 14. Find the output for this code? public class Deccansoft { public static void main(String[] args) { HashMap obj= new HashMap(); obj.put("A", new Integer(1)); obj.put("B", new Integer("hello")); obj.put("C", new Integer(5)); System.out.println(obj); } }

19. 19.Find the output for this code? Class Deccansoft { public static void main(String args[]) { ListIterator a =List.listIterator(); if(a.previousIndex()!=-1) while(a.hasNext()) System.out.println(a.next()+” ”); else System.out.print(“empty”); } }

24. 24. Collection stores only ?

25. 25.Which type of exception is thrown if you try to add an element to an already full Collection ?

26. 26. Which interface does NavigableSet implements ?

27. 27. What does get(int index) method define by List interface do ?

28. 28. Which of the following interface guarantees that no duplicates elements are stored and all elements are accessed in natural order ?

29. 29. Which of the following statement is not true about ArrayList class ?

30. 30. Which of the following statement is true about TreeSet class ?

31. 31. Which class does java.util.Properties extends ?

32. 32. Which interface is used to traverse a list in both forward and backward direction ?

33. 33. Which interface provides the capability to store objects using a key-value pair ?

34. 34. Which of the following method is used to return a Set that contains the entries in a map ?

35. 35. Which of the following statement is not correct about HashMap class ?

36. 36. Which of the following class provide the facility to specify default value that is used when no value is associated with a certain key ?

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