Java Collections Framework MCQ PDF

**Q:-1 What is the purpose of the Collections Framework?** **A.To provide a unified architecture for representing and manipulating collections** **B.To provide a way to create arrays** **C.To define primitive data types** **D.To handle exceptions** **Ans:-A.** **2:-Which interface in the Java...

**Q:-1 What is the purpose of the Collections Framework?** **A.To provide a unified architecture for representing and manipulating collections** **B.To provide a way to create arrays** **C.To define primitive data types** **D.To handle exceptions** **Ans:-A.** **2:-Which interface in the Java Collections Framework represents an ordered collection of elements that can contain duplicate values?** **A.\`Collection\`** **B.\`Map\`** **C.\`Set\`** **D.\`List\`** **Ans:-D** **Q:-3 What is the primary difference between a \`List\` and a \`Set\` in the Java Collections Framework?** **A. A \`Set\` allows duplicate elements, while a \`List\` does not** **B. A \`List\` is unmodifiable, while a \`Set\` is modifiable** **C. A \`List\` allows duplicate elements, while a \`Set\` does not** **D. A \`Set\` is indexed, while a \`List\` is not** **Answer: Option C** **Q:-4 Which class is typically used to implement a \`List\` in the Java Collections Framework?** **A. \`HashMap\`** **B. \`ArrayList\`** **C. \`LinkedList\`** **D. None of These** **Answer: Option B** **Q:-5 In the Java Collections Framework, which interface extends the \`List\` interface to provide more efficient insertions and deletions in the middle of the list?** **A. \`Map\`** **B. \`Set\`** **C. \`Deque\`** **D. \`Queue\`** **Answer: Option C** **Q:-6 What is the purpose of the \`Map\` interface in the Java Collections Framework?** **A. To store a collection of objects** **B. To provide a stack data structure** **C. To store unique elements** **D. To store key-value pairs** **Answer: Option D** **Q:-7 Which class is typically used to implement a \`Map\` in the Java Collections Framework?** **A. \`HashMap\`** **B. \`ArrayList\`** **C. \`HashSet\`** **D. \`LinkedList\`** **Answer: Option A** **Q:- 8 What is the primary difference between a \`HashMap\` and a \`TreeMap\` in the Java Collections Framework?** **A. A \`TreeMap\` uses a linked list to store elements** **B. A \`HashMap\` is synchronized, while a \`TreeMap\` is not** **C. A \`TreeMap\` allows duplicate keys, while a \`HashMap\` does not** **D. A \`HashMap\` does not maintain order, while a \`TreeMap\` does** **Answer: Option D** **Q:-9 In the Java Collections Framework, which interface represents a collection of unique elements with no duplicates?** **A. \`List\`** **B. \`Map\`** **C. \`Set\`** **D. \`Collection\`** **Answer: Option C** **Q:-10 Which class is typically used to implement a \`Set\` in the Java Collections Framework?** **A. \`HashMap\`** **B. \`HashSet\`** **C. \`LinkedList\`** **D. None of These** **Answer: Option B** **Q:-11 What is the primary difference between a \`HashSet\` and a \`LinkedHashSet\` in the Java Collections Framework?** **A. A \`HashSet\` uses a tree structure to store elements** **B. A \`LinkedHashSet\` is synchronized, while a \`HashSet\` is not** **C. A \`LinkedHashSet\` maintains insertion order, while a \`HashSet\` does not** **D. A \`HashSet\` allows duplicate elements, while a \`LinkedHashSet\` does not** **Answer: Option C** **Q:-12 Which interface in the Java Collections Framework represents a collection of elements with no specific order?** **A. \`List\`** **B. \`Map\`** **C. \`Collection\`** **D. \`Set\`** **Answer: Option D** **Q:-13 What is the primary difference between a \`Queue\` and a \`Deque\` in the Java Collections Framework?** **A. A \`Queue\` represents a single-ended queue, while a \`Deque\` represents a double-ended queue** **B. A \`Queue\` allows duplicate elements, while a \`Deque\` does not** **C. A \`Deque\` is synchronized, while a \`Queue\` is not** **D. A \`Queue\` is indexed, while a \`Deque\` is not** **Answer: Option A** **Q:-14 Which class is typically used to implement a \`Deque\` in the Java Collections Framework?** **A. \`LinkedList\`** **B. \`HashMap\`** **C. \`HashSet\`** **D. \`ArrayDeque\`** **Answer: Option D** **Q:-15 In the Java Collections Framework, which class allows you to create a synchronized (thread-safe) collection?** **A. \`ArrayList\`** **B. \`HashMap\`** **C. \`Collections\`** **D. \`HashSet\`** **Answer: Option C** **Q:- 16 Which interface in the Java Collections Framework extends the \`Set\` interface and represents a collection of elements stored in a sorted order?** **A. \`Map\`** **B. \`SortedSet\`** **C. \`Queue\`** **D. None of These** **Answer: Option B** **Q:-17 What is the purpose of the \`Comparator\` interface in Java Collections Framework?** **A. It represents a generic collection** **B. It provides methods for hashing elements** **C. It defines a comparison function for ordering elements** **D. It represents a synchronized collection** **Answer: Option C** **Q:-18 Which class is typically used to implement a \`SortedSet\` in the Java Collections Framework?** **A. \`HashSet\`** **B. \`LinkedHashSet\`** **C. \`ArrayList\`** **D. \`TreeSet\`** **Answer: Option D** **Q:-19 In the Java Collections Framework, which interface represents a last-in, first-out (LIFO) stack of elements?** **A. \`Stack\`** **B. \`Queue\`** **C. \`List\`** **D. \`Deque\`** **Answer: Option A** **Q:-20 What is the primary difference between a \`Stack\` and a \`Queue\` in the Java Collections Framework?** **A. A \`Queue\` allows duplicate elements, while a \`Stack\` does not** **B. A \`Stack\` allows duplicate elements, while a \`Queue\` does not** **C. A \`Queue\` uses a LIFO order, while a \`Stack\` uses a FIFO order** **D. A \`Stack\` uses a LIFO (Last-In-First-Out) order, while a \`Queue\` uses a FIFO (First-In-First-Out) order** **Answer: Option D** **Q:-21 In Java, which method is used to add an element to a collection in the Java Collections Framework?** **A. \`insert()\`** **B. \`put()\`** **C. \`add()\`** **D. \`append()\`** **Answer: Option C** **Q:-22 What is the purpose of the \`toArray()\` method in the Java Collections Framework?** **A. It sorts the collection** **B. It converts a collection to an array** **C. It reverses the collection** **D. None of These** **Answer: Option B** **Q:-23 In the Java Collections Framework, which class provides methods to manipulate the size of a list and its elements?** **A. \`Set\`** **B. \`ArrayList\`** **C. \`Collections\`** **D. \`List\`** **Answer: Option C** **Q:-24 What is the purpose of the \`Iterator\` interface in the Java Collections Framework?** **A. It defines a comparison function for ordering elements** **B. It represents a synchronized collection** **C. It provides methods for hashing elements** **D. It provides a way to iterate over a collection\'s elements** **Answer: Option D** **Q:-25 Which method is used to remove all elements from a collection in the Java Collections Framework?** **A. \`clear()\`** **B. \`removeAll()\`** **C. \`erase()\`** **D. \`purge()\`** **Answer: Option A** **Q:-26 What is the purpose of the \`Map.Entry\` interface in the Java Collections Framework?** **A. It provides methods for hashing elements** **B. It represents a synchronized collection** **C. It defines a comparison function for ordering elements** **D. It represents a key-value pair in a map** **Answer: Option D** **Q:-27 In the Java Collections Framework, which method is used to obtain a synchronized (thread-safe) version of a collection?** **A. \`synchronize()\`** **B. \`synchronizedList()\`** **C. \`Collections.synchronizedCollection()\`** **D. \`makeSynchronized()\`** **Answer: Option C** **Q:-28 What is the primary difference between a \`HashSet\` and a \`LinkedHashSet\` in the Java Collections Framework?** **A. A \`LinkedHashSet\` allows duplicate elements, while a \`HashSet\` does not** **B. A \`LinkedHashSet\` maintains the insertion order of elements, while a \`HashSet\` does not** **C. A \`HashSet\` allows duplicate elements, while a \`LinkedHashSet\` does not** **D. None of These** **Answer: Option B** **Q:-29 In Java, which method is used to obtain a synchronized (thread-safe) map from an existing map in the Java Collections Framework?** **A. \`makeSynchronizedMap()\`** **B. \`synchronized()\`** **C. \`Collections.synchronizedMap()\`** **D. \`synchronizeMap()\`** **Answer: Option C** **Q:-30 What is the purpose of the \`Collections.reverse()\` method in the Java Collections Framework?** **A. It removes all elements from a list** **B. It sorts a list in ascending order** **C. It adds elements to a list** **D. It reverses the order of elements in a list** **Answer: Option D** **Q:-31 Which of these method can be used to increase the capacity of ArrayList object manually?** **A. Capacity()** **B. increaseCapacity()** **C. increasecapacity()** **D. ensureCapacity()** **Answer: Option D** **Q:-32 What will be the output of the following Java code snippet?** **import java.util.\*;** **class Linkedlist** **{** **public static void main(String args\[\])** **{** **LinkedList obj = new LinkedList();** **obj.add(\"A\");** **obj.add(\"B\");** **obj.add(\"C\");** **obj.addFirst(\"D\");** **System.out.println(obj);** **}** **}** **A. \[A, B, C\]** **B. \[D, B, C\]** **C. \[A, B, C, D\]** **D. \[D, A, B, C\]** **Answer: Option D** **Q:-33 What is Collection in Java?** **A. A group of objects** **B. A group of classes** **C. A group of interfaces** **D. None of the mentioned** **Answer: Option A** **Q:-34 Which of these methods can convert an object into a List?** **A. SetList()** **B. ConvertList()** **C. singletonList()** **D. CopyList()** **Answer: Option C** **Q:-35 What will be the output of the following Java program?** **import java.util.\*;** **class Maps** **{** **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));** **System.out.println(obj.get(\"B\"));** **}** **}** **A. 1** **B. 2** **C. 3** **D. null** **Answer: Option B** **Q:-36 What is the premise of equality for IdentityHashMap?** **A. Reference equality** **B. Name equality** **C. Hashcode equality** **D. Length equality** **Answer: Option A** **Q:-37 Which of these is static variable defined in Collections?** **A. EMPTY\_SET** **B. EMPTY\_LIST** **C. EMPTY\_MAP** **D. All of the mentioned** **Answer: Option D** **Q:-38 Which of these methods is used to add elements in vector at specific location?** **A. add()** **B. set()** **C. AddElement()** **D. addElement()** **Answer: Option D** **Q:-39 What will be the output of the following Java program?** **import java.util.\*;** **class Collection\_Algos** **{** **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);** **Collections.sort(list);** **while(i.hasNext())** **System.out.print(i.next() + \" \");** **}** **}** **A. 2 8 5 1** **B. 1 5 8 2** **C. 1 2 5 8** **D. 2 1 8 5** **Answer: Option C** **Q:-40 What is the difference between Queue and Stack?** **A. Stack is LIFO; Queue is FIFO** **B. Queue is LIFO; Stack is FIFO** **C. Stack and Queue is FIFO** **D. Stack and Queue is LIFO** **Answer: Option A** **Q:-41 What will be the output of the following Java code?** **import java.util.\*;** **class Bitset** **{** **public static void main(String args\[\])** **{** **BitSet obj1 = new BitSet(5);** **BitSet obj2 = new BitSet(10);** **for (int i = 0; i \< 5; ++i)** **obj1.set(i);** **for (int i = 3; i \< 13; ++i)** **obj2.set(i);** **obj1.and(obj2);** **System.out.print(obj1);** **}** **}** **A. {0, 1}** **B. {2, 4}** **C. {3, 4}** **D. {3, 4, 5}** **Answer: Option C** **Q:-42 What are the use of front and rear pointers in CircularQueue implementation?** **A. Front pointer points to first element; rear pointer points to the last element** **B. Rear pointer points to first element; front pointer points to the last element** **C. Front and read pointers point to the first element** **D. Front pointer points to the first element; rear pointer points to null object** **Answer: Option C** **Q:-43 Which of the below is not a subinterface of Queue?** **A. BlockingQueue** **B. BlockingEnque** **C. TransferQueue** **D. None of These** **Answer: Option B** **Q:-44 Which of these method is used to reduce the capacity of an ArrayList object?** **A. trim()** **B. trimSize()** **C. trimTosize()** **D. trimToSize()** **Answer: Option D** **Q:-45 How to sort elements of ArrayList?** **A. Collection.sort(listObj);** **B. Collections.sort(listObj);** **C. listObj.sort();** **D. Sorter.sortAsc(listObj);** **Answer: Option B** **Q:-46 Which of these packages contain all the collection classes?** **A. java.lang** **B. java.util** **C. java.net** **D. java.awt** **Answer: Option B** **Q:-47 Which of these methods can be used to obtain set of all keys in a map?** **A. getAll()** **B. getKeys()** **C. keyall()** **D. keySet()** **Answer: Option D** **Q:-48 Which of these methods are member of Remote class?** **A. checkIP()** **B. addLocation()** **C. AddServer()** **D. None of the mentioned** **Answer: Option D** **Q:-49 Which of these method Map class is used to obtain an element in the map having specified key?** **A. search()** **B. get()** **C. set()** **D. look()** **Answer: Option B** **Q:-50 What is the name of a data member of class Vector which is used to store a number of elements in the vector?** **A. length** **B. elements** **C. elementCount** **D. capacity** **Answer: Option C** **Q:-51 What will be the output of the following Java program?** **import java.util.\*;** **class Maps** **{** **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));** **System.out.println(obj.keySet());** **}** **}** **A. \[A, B, C\]** **B. {A, B, C}** **C. {1, 2, 3}** **D. \[1, 2, 3\]** **Answer: Option A** **Q:-52 What will be the output of the following Java code?** **import java.util.\*;** **class date** **{** **public static void main(String args\[\])** **{** **Date obj = new Date();** **System.out.print(obj);** **}** **}** **A. Prints Present Date** **B. Runtime Error** **C. Any Garbage Value** **D. Prints Present Time & Date** **Answer: Option D** **Q:-53 What is the worst case complexity of accessing an element in ArrayList?** **A. O(n)** **B. O(1)** **C. O(nlogn)** **D. O(2)** **Answer: Option B** **Q:-54 Which of these standard collection classes implements a dynamic array?** **A. AbstractList** **B. LinkedList** **C. ArrayList** **D. AbstractSet** **Answer: Option C** **Q:-55 What is the correct method used to insert and delete items from the queue?** **A. push and pop** **B. enqueue and dequeue** **C. enqueue and peek** **D. add and remove** **Answer: Option B** **Q:-56 Which of these standard collection classes implements all the standard functions on list data structure?** **A. Array** **B. LinkedList** **C. HashSet** **D. AbstractSet** **Answer: Option A** **Q:-57 What happens if two threads simultaneously modify TreeSet?** **A. ConcurrentModificationException is thrown** **B. Both threads can perform action successfully** **C. FailFastException is thrown** **D. IteratorModificationException is thrown** **Answer: Option A** **Q:-59 What will be the output of the following Java code snippet?\ ** **public class Test** **{** **public static void main(String\[\] args)** **{** **Set s = new HashSet();** **s.add(new Long(10));** **s.add(new Integer(10));** **for(Object object : s)** **{** **System.out.println(\"test - \"+object);** **}** **}** **}** **A. Test - 10\ Test - 10** **B. Test - 10** **C. Runtime Exception** **D. Compilation Failure** **Answer: Option A** **Q:-60 Which of these is the interface of legacy?** **A. Map** **B. Enumeration** **C. HashMap** **D. Hashtable** **Answer: Option B** **Q:-61 What will be the output of the following Java code?\ ** **import java.util.\*;** **class hashtable** **{** **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));** **System.out.print(obj.contains(new Integer(5)));** **}** **}** **A. 0** **B. 1** **C. true** **D. false** **Answer: Option D** **Which of the below is not an implementation of List interface?** **A. RoleUnresolvedList** **B. Stack** **C. AttibuteList** **D. SessionList** **Answer: Option D** **Q:-62 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** **Answer: Option B** **Q:-63 Which of these is a Basic interface that all other interface inherits?** **A. Set** **B. Array** **C. List** **D. Collection** **Answer: Option D** **Q:-64 Which of these is a method of ListIterator used to obtain index of previous element?** **A. previous()** **B. previousIndex()** **C. back()** **D. goBack()** **Answer: Option B** **Q:-65 What will be the output of the following Java program?\ ** **import java.util.\*;** **class Arraylist** **{** **public static void main(String args\[\])** **{** **ArrayList obj = new ArrayList();** **obj.add(\"A\");** **obj.add(\"B\");** **obj.add(\"C\");** **obj.add(1, \"D\");** **System.out.println(obj);** **}** **}** **A. \[A, B, C, D\]** **B. \[A, D, B, C\]** **C. \[A, D, C\]** **D. \[A, B, C\]** **Answer: Option B** **Q:-66 What will be the output of the following Java program?\ ** **import java.util.\*;** **class Maps** **{** **public static void main(String args\[\])** **{** **TreeMap obj = new TreeMap();** **obj.put(\"A\", new Integer(1));** **obj.put(\"B\", new Integer(2));** **obj.put(\"C\", new Integer(3));** **System.out.println(obj.entrySet());** **}** **}** **A. \[A, B, C\]** **B. \[1, 2, 3\]** **C. {A=1, B=2, C=3}** **D. \[A=1, B=2, C=3\]** **Answer: Option D** **Q:-67 Which of these method is used to calculate number of bits required to hold the BitSet object?** **A. size()** **B. length()** **C. indexes()** **D. numberofBits()** **Answer: Option B** **Q:-68 Which of these Exceptions is thrown by remote method?** **A. RemoteException** **B. InputOutputException** **C. RemoteAccessException** **D. RemoteInputOutputException** **Answer: Option A** **Q:-69 Which of these class object has an architecture similar to that of array?** **A. Bitset** **B. Map** **C. Hashtable** **D. All of the mentioned** **Answer: Option A** **Q:-70 Which of these method of Array class is used sort an array or its subset?** **A. binarysort()** **B. bubblesort()** **C. sort()** **D. insert()** **Answer: Option C** **Q:-71 What will be the output of the following Java code?\ ** **import java.util.\*;** **class hashtable** **{** **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));** **System.out.print(obj.toString());** **}** **}** **A. {C=8, B=2}** **B. \[C=8, B=2\]** **C. {A=3, C=8, B=2}** **D. \[A=3, C=8, B=2\]** **Answer: Option C** **Q:-72 Which of these is the interface of legacy is implemented by Hashtable and Dictionary classes?** **A. Map** **B. Enumeration** **C. HashMap** **D. Hashtable** **Answer: Option A** **Q:-73 What will be the output of the following Java program?\ ** **import java.util.\*;** **class Array** **{** **public static void main(String args\[\])** **{** **int array\[\] = new int \[5\];** **for (int i = 5; i \> 0; i\--)** **array\[5 - i\] = i;** **Arrays.sort(array);** **for (int i = 0; i \< 5; ++i)** **System.out.print(array\[i\]);;** **}** **}** **A. 12345** **B. 54321** **C. 1234** **D. 5432** **Answer: Option A** **Q:-74 What is the unique feature of LinkedHashSet?** **A. It is not a valid class** **B. It maintains the insertion order and guarantees uniqueness** **C. It provides a way to store key values with uniqueness** **D. The elements in the collection are linked to each other** **Answer: Option B** **Q:-75 What will be the output of the following Java program?\ ** **import java.util.\*;** **class Arraylist** **{** **public static void main(String args\[\])** **{** **ArrayList obj1 = new ArrayList();** **ArrayList obj2 = new ArrayList();** **obj1.add(\"A\");** **obj1.add(\"B\");** **obj2.add(\"A\");** **obj2.add(1, \"B\");** **System.out.println(obj1.equals(obj2));** **}** **}** **A. 0** **B. 1** **C. true** **D. false** **Answer: Option C** **Q:-76 What will be the output of the following Java program?\ ** **import java.util.\*;** **class Maps** **{** **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));** **System.out.println(obj);** **}** **}** **A. {A 1, B 1, C 1}** **B. {A, B, C}** **C. {A-1, B-1, C-1}** **D. {A=1, B=2, C=3}** **Answer: Option D** **Q:-77 Which of these class object uses the key to store value?** **A. Dictionary** **B. Map** **C. Hashtable** **D. All of the mentioned** **Answer: Option D** **Q:-78 Which of these class object can be used to form a dynamic array?** **A. ArrayList** **B. Map** **C. Vector** **D. ArrayList & Vector** **Answer: Option D** **Q:-79 What will be the output of the following Java program?\ ** **import java.util.\*;** **class Collection\_Algos** **{** **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);** **while(i.hasNext())** **System.out.print(i.next() + \" \");** **}** **}** **A. 2 8 5 1** **B. 1 5 8 2** **C. 2** **D. 2 1 8 5** **Answer: Option B** **Q:-80 What will be the output of the following Java code?\ ** **import java.util.\*;** **class vector** **{** **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));** **System.out.println(obj.elementAt(1));** **}** **}** **A. 0** **B. 3** **C. 2** **D. 5** **Answer: Option C** **Q:-81 What will be the output of the following Java code?\ ** **import java.util.\*;** **class stack** **{** **public static void main(String args\[\])** **{** **Stack obj = new Stack();** **obj.push(new Integer(3));** **obj.push(new Integer(2));** **obj.pop();** **obj.push(new Integer(5));** **System.out.println(obj);** **}** **}** **A. \[3, 5\]** **B. \[3, 2\]** **C. \[3, 2, 5\]** **D. \[3, 5, 2\]** **Answer: Option A** **Q:-82 Which of these methods can randomize all elements in a list?** **A. rand()** **B. randomize()** **C. shuffle()** **D. ambiguous()** **Answer: Option C** **Q:-83 Which of these methods can be used to obtain a static array from an ArrayList object?** **A. Array()** **B. covertArray()** **C. toArray()** **D. covertoArray()** **Answer: Option C** **Q:-84 Which of these method is used to insert value and its key?** **A. put()** **B. set()** **C. insertElement()** **D. addElement()** **Answer: Option A** **Q:-85 Which of these method is used to remove all keys/values pair from the invoking map?** **A. delete()** **B. remove()** **C. clear()** **D. removeAll()** **Answer: Option B** **Q:-86 What will be the output of the following Java program?\ ** **import java.util.\*;** **class Collection\_iterators** **{** **public static void main(String args\[\])** **{** **ListIterator a = list.listIterator();** **if(a.previousIndex()! = -1)** **while(a.hasNext())** **System.out.print(a.next() + \" \");** **else** **System.out.print(\"EMPTY\");** **}** **}** **A. 0** **B. 1** **C. -1** **D. EMPTY** **Answer: Option D** **Q:-87 What will be the output of the following Java program?\ ** **import java.lang.reflect.\*;** **class Additional\_packages** **{** **public static void main(String args\[\])** **{** **try** **{** **Class c = Class.forName(\"java.awt.Dimension\");** **Method methods\[\] = c.getMethods();** **for (int i = 0; i \< methods.length; i++)** **System.out.println(methods\[i\]);** **}** **catch (Exception e)** **{** **System.out.print(\"Exception\");** **}** **}** **}** **A. Program prints all the constructors of \'java.awt.Dimension\' package** **B. Program prints all the methods of \'java.awt.Dimension\' package** **C. Program prints all the data members of \'java.awt.Dimension\' package** **D. program prints all the methods and data member of \'java.awt.Dimension\' package** **Answer: Option B** **Q:-88 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** **Answer: Option A** **Q:-89 Which of these interface handle sequences?** **A. Set** **B. List** **C. Comparator** **D. Collection** **Answer: Option B** **Q:-90 How to externally synchronize hashmap?** **A. HashMap.synchronize(HashMap a);** **B. HashMap a = new HashMap();\ a.synchronize();** **C. Collections.synchronizedMap(new HashMap\());** **D. Collections.synchronize(new HashMap\());** **Answer: Option C** **Q:-91 Set has contains(Object o) method.** **A. True** **B. False** **Answer: Option A** **Q:-92 What is the relation between hashset and hashmap?** **A. HashSet internally implements HashMap** **B. HashMap internally implements HashSet** **C. HashMap is the interface; HashSet is the concrete class** **D. HashSet is the interface; HashMap is the concrete class** **Answer: Option A** **Q:-93 Which of these return type of hasNext() method of an iterator?** **A. Integer** **B. Double** **C. Boolean** **D. Collections Object** **Answer: Option C** **Q:-94 Which of these is an incorrect form of using method max() to obtain a maximum element?** **A. max(Collection c)** **B. max(Collection c, Comparator comp)** **C. max(Comparator comp)** **D. max(List c)** **Answer: Option C** **Q:-95 Which of these methods is used to obtain an iterator to the start of collection?** **A. start()** **B. begin()** **C. iteratorSet()** **D. iterator()** **Answer: Option D** **Q:-96 What will be the output of the following Java program?\ ** **import java.util.\*;** **class Output** **{** **public static void main(String args\[\])** **{** **TreeSet t = new TreeSet();** **t.add(\"3\");** **t.add(\"9\");** **t.add(\"1\");** **t.add(\"4\");** **t.add(\"8\");** **System.out.println(t);** **}** **}** **A. \[1, 3, 5, 8, 9\]** **B. \[3, 4, 1, 8, 9\]** **C. \[9, 8, 4, 3, 1\]** **D. \[1, 3, 4, 8, 9\]** **Answer: Option D** **Q:-97 What will be the output of the following Java program?\ ** **import java.util.\*;** **class Array** **{** **public static void main(String args\[\])** **{** **int array\[\] = new int \[5\];** **for (int i = 5; i \> 0; i\--)** **array\[5-i\] = i;** **Arrays.fill(array, 1, 4, 8);** **for (int i = 0; i \< 5 ; i++)** **System.out.print(array\[i\]);** **}** **}** **A. 12885** **B. 12845** **C. 58881** **D. 54881** **Answer: Option C** **Q:-98 What will be the output of the following Java code?\ ** **import java.util.\*;** **class hashtable** **{** **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.clear();** **System.out.print(obj.size());** **}** **}** **A. 0** **B. 1** **C. 2** **D. 3** **Answer: Option A** **Q:-99 Which of these methods is used to retrieve the elements in properties object at specific location?** **A. get()** **B. Elementat()** **C. ElementAt()** **D. getProperty()** **Answer: Option D** **Q:-100 Set has contains(Object o) method.** **A. True** **B. False** **Answer: Option A** **Q:-101 What is the relation between hashset and hashmap?** **A. HashSet internally implements HashMap** **B. HashMap internally implements HashSet** **C. HashMap is the interface; HashSet is the concrete class** **D. HashSet is the interface; HashMap is the concrete class** **Answer: Option A** **Q:-102 Which of these return type of hasNext() method of an iterator?** **A. Integer** **B. Double** **C. Boolean** **D. Collections Object** **Answer: Option C** **Q:-103 Which of these methods is used to obtain an iterator to the start of collection?** **A. start()** **B. begin()** **C. iteratorSet()** **D. iterator()** **Answer: Option D** **Q:-104 What will be the output of the following Java program?\ ** **import java.util.\*;** **class Output** **{** **public static void main(String args\[\])** **{** **TreeSet t = new TreeSet();** **t.add(\"3\");** **t.add(\"9\");** **t.add(\"1\");** **t.add(\"4\");** **t.add(\"8\");** **System.out.println(t);** **}** **}** **A. \[1, 3, 5, 8, 9\]** **B. \[3, 4, 1, 8, 9\]** **C. \[9, 8, 4, 3, 1\]** **D. \[1, 3, 4, 8, 9\]** **Answer: Option D** **Q:-105 What will be the output of the following Java program?\ ** **import java.util.\*;** **class Array** **{** **public static void main(String args\[\])** **{** **int array\[\] = new int \[5\];** **for (int i = 5; i \> 0; i\--)** **array\[5-i\] = i;** **Arrays.fill(array, 1, 4, 8);** **for (int i = 0; i \< 5 ; i++)** **System.out.print(array\[i\]);** **}** **}** **A. 12885** **B. 12845** **C. 58881** **D. 54881** **Answer: Option C** **Q:-106 What will be the output of the following Java code?\ ** **import java.util.\*;** **class hashtable** **{** **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.clear();** **System.out.print(obj.size());** **}** **}** **A. 0** **B. 1** **C. 2** **D. 3** **Answer: Option A** **Q:-107 Which of these methods is used to retrieve the elements in properties object at specific location?** **A. get()** **B. Elementat()** **C. ElementAt()** **D. getProperty()** **Answer: Option D** **Q:-108 Which of these method is used add an element and corresponding key to a map?** **A. put()** **B. set()** **C. redo()** **D. add()** **Answer: Option A** **Q:-109 How to remove duplicates from List?** **A. HashSet\ listToSet = new HashSet\(duplicateList);** **B. HashSet\ listToSet = duplicateList.toSet();** **C. HashSet\ listToSet = Collections.convertToSet(duplicateList);** **D. HashSet\ listToSet = duplicateList.getSet();** **Answer: Option A** **110 Which of these iterators can be used only with List?** **A. Setiterator** **B. ListIterator** **C. Literator** **D. None of the mentioned** **Answer: Option B** **111 Is hashmap an ordered collection.** **A. True** **B. False** **Answer: Option B** **112 How is Arrays.asList() different than the standard way of initialising List?** **A. Both are same** **B. Arrays.asList() throws compilation error** **C. Arrays.asList() returns a fixed length list and doesn\'t allow to add or remove elements** **D. We cannot access the list returned using Arrays.asList()** **Answer: Option C** **113 What is difference between dequeue() and peek() function of java?** **A. dequeue() and peek() remove and return the next time in line** **B. dequeue() and peek() return the next item in line** **C. dequeue() removes and returns the next item in line while peek() returns the next item in line** **D. peek() removes and returns the next item in line while dequeue() returns the next item in line** **Answer: Option C** **114 Which of these method of ArrayList class is used to obtain present size of an object?** **A. size()** **B. length()** **C. index()** **D. capacity()** **Answer: Option A** **115 Which of these are legacy classes?** **A. Stack** **B. Hashtable** **C. Vector** **D. All of the mentioned** **Answer: Option D** **116 What are the initial capacity and load factor of HashSet?** **A. 10, 1.0** **B. 32, 0.75** **C. 16, 0.75** **D. 32, 1.0** **Answer: Option C** **117 What will be the output of the following Java program?\ ** **import java.util.\*;** **class Collection\_Algos** **{** **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();** **while(i.hasNext())** **System.out.print(i.next() + \" \");** **}** **}** **A. 2 8 5 1** **B. 1 5 8 2** **C. 2** **D. 2 1 8 5** **Answer: Option A** **118 What will be the output of the following Java program?\ ** **import java.util.\*;** **class Output** **{** **public static void main(String args\[\])** **{** **HashSet obj = new HashSet();** **obj.add(\"A\");** **obj.add(\"B\");** **obj.add(\"C\");** **System.out.println(obj + \" \" + obj.size());** **}** **}** **A. ABC 3** **B. \[A, B, C\] 3** **C. ABC 2** **D. \[A, B, C\] 2** **Answer: Option B** **119 Do we have get(Object o) method in HashSet.** **A. True** **B. False** **Answer: Option B** **120 Which of these standard collection classes implements a linked list data structure?** **A. AbstractList** **B. LinkedList** **C. HashSet** **D. AbstractSet** **Answer: Option B** **121 Which of these methods deletes all the elements from invoking collection?** **A. clear()** **B. reset()** **C. delete()** **D. refresh()** **Answer: Option A** **122 What does Collections.emptySet() return?** **A. Immutable Set** **B. Mutable Set** **C. The type of Set depends on the parameter passed to the emptySet() method** **D. Null object** **Answer: Option A** **123 What will be the output of the following Java code snippet?\ ** **public class Demo** **{** **public static void main(String\[\] args)** **{** **Map sampleMap = new TreeMap();** **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}** **Answer: Option A** **124 What will be the output of the following Java code?\ ** **import java.util.\*;** **class vector** **{** **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));** **System.out.println(obj.capacity());** **}** **}** **A. 2** **B. 3** **C. 4** **D. 6** **Answer: Option C** **125 Which of these object stores association between keys and values?** **A. Hash table** **B. Map** **C. Array** **D. String** **Answer: Option B** **126 What will be the output of the following Java program?\ ** **import java.util.\*;** **class Collection\_iterators** **{** **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);** **while(i.hasNext())** **System.out.print(i.next() + \" \");** **}** **}** **A. 2 8 5 1** **B. 1 5 8 2** **C. 2** **D. 2 1 8 5** **Answer: Option B** **127 Which of these methods can be used to search an element in a list?** **A. find()** **B. sort()** **C. get()** **D. binaryserach()** **Answer: Option D** **128 How can we remove an object from ArrayList?** **A. remove() method** **B. using Iterator** **C. remove() method and using Iterator** **D. delete() method** **Answer: Option C** **129 What will be the output of the following Java program?\ ** **import java.util.\*;** **class Output** **{** **public static void main(String args\[\])** **{** **ArrayList obj = new ArrayList();** **obj.add(\"A\");** **obj.ensureCapacity(3);** **System.out.println(obj.size());** **}** **}** **A. 1** **B. 2** **C. 3** **D. 4** **Answer: Option A** **130 What will be the output of the following Java program?\ ** **import java.util.\*;** **class Array** **{** **public static void main(String args\[\])** **{** **int array\[\] = new int \[5\];** **for (int i = 5; i \> 0; i\--)** **array\[5 - i\] = i;** **Arrays.sort(array);** **for (int i = 0; i \< 5; ++i)** **System.out.print(array\[i\]);;** **}** **}** **A. 12345** **B. 54321** **C. 1234** **D. 5432** **Answer: Option A** **131 Which of these methods can be used to move to next element in a collection?** **A. next()** **B. move()** **C. shuffle()** **D. hasNext()** **Answer: Option A** **134 Which of this method is used to change an element in a LinkedList Object?** **A. change()** **B. set()** **C. redo()** **D. add()** **Answer: Option B** **135 What will be the output of the following Java program?\ ** **import java.util.\*;** **class Linkedlist** **{** **public static void main(String args\[\])** **{** **LinkedList obj = new LinkedList();** **obj.add(\"A\");** **obj.add(\"B\");** **obj.add(\"C\");** **obj.removeFirst();** **System.out.println(obj);** **}** **}** **A. \[A, B\]** **B. \[B, C\]** **C. \[A, B, C, D\]** **D. \[A, B, C\]** **Answer: Option B** **136 What will be the output of the following Java code?\ ** **import java.util.\*;** **class vector** **{** **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());** **}** **}** **A. 0** **B. 1** **C. true** **D. false** **Answer: Option C** **137 What will be the output of the following Java code?\ ** **import java.util.\*;** **class hashtable** **{** **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.print(obj);** **}** **}** **A. {C=8, B=2}** **B. \[C=8, B=2\]** **C. {A=3, C=8, B=2}** **D. \[A=3, C=8, B=2\]** **Answer: Option A** **138 Which of these classes implements Set interface?** **A. ArrayList** **B. HashSet** **C. LinkedList** **D. DynamicList** **Answer: Option B** **139 Which of this interface is not a part of Java\'s collection framework?** **A. List** **B. Set** **C. SortedMap** **D. SortedList** **Answer: Option D** **140 Which of this method is used to make all elements of an equal to specified value?** **A. add()** **B. fill()** **C. all()** **D. set()** **Answer: Option B** **141 Which of these interface declares core method that all collections will have?** **A. set** **B. EventListner** **C. Comparator** **D. Collection** **Answer: Option D** **142 What is the difference between TreeSet and SortedSet?** **A. TreeSet is more efficient than SortedSet** **B. SortedSet is more efficient than TreeSet** **C. TreeSet is an interface; SortedSet is a concrete class** **D. SortedSet is an interface; TreeSet is a concrete class** **Answer: Option D** **143 Map implements collection interface?** **A. True** **B. False** **Answer: Option B** **144 What will be the output of the following Java program?\ ** **import java.util.\*;** **class Collection\_Algos** **{** **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);** **Collections.shuffle(list);** **while(i.hasNext())** **System.out.print(i.next() + \" \");** **}** **}** **A. 2 8 5 1** **B. 1 5 8 2** **C. 1 2 5 8** **D. Any random order** **Answer: Option D** **145 What will be the output of the following Java code?\ ** **import java.util.\*;** **class vector** **{** **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(6));** **obj.insertElementAt(new Integer(8), 2);** **System.out.println(obj);** **}** **}** **A. \[3, 2, 6\]** **B. \[3, 2, 8\]** **C. \[3, 2, 6, 8\]** **D. \[3, 2, 8, 6\]** **Answer: Option D** **146 Which of these methods sets every element of a List to a specified object?** **A. set()** **B. fill()** **C. Complete()** **D. add()** **Answer: Option B** **147 Which of these methods can be used to delete the last element in a LinkedList object?** **A. remove()** **B. delete()** **C. removeLast()** **D. deleteLast()** **Answer: Option C** **148 Which of these method is used to add an element to the start of a LinkedList object?** **A. add()** **B. first()** **C. AddFirst()** **D. addFirst()** **Answer: Option D** **149 What will be the output of the following Java code?\ ** **import java.util.\*;** **class properties** **{** **public static void main(String args\[\])** **{** **Properties obj = new Properties();** **obj.put(\"AB\", new Integer(3));** **obj.put(\"BC\", new Integer(2));** **obj.put(\"CD\", new Integer(8));** **System.out.print(obj.keySet());** **}** **}** **A. {AB, BC, CD}** **B. \[AB, BC, CD\]** **C. \[3, 2, 8\]** **D. {3, 2, 8}** **Answer: Option B** **150 Which of the below does not implement Map interface?** **A. HashMap** **B. Hashtable** **C. EnumMap** **D. Vector** **Answer: Option D** **151 Which of these classes provide implementation of map interface?** **A. ArrayList** **B. HashMap** **C. LinkedList** **D. DynamicList** **Answer: Option B** **152 Which of these methods is used to retrieve elements in BitSet object at specific location?** **A. get()** **B. Elementat()** **C. ElementAt()** **D. getProperty()** **Answer: Option A** **153 Which of these exceptions is thrown by remover() method?** **A. IOException** **B. SystemException** **C. ObjectNotFoundExeception** **D. IllegalStateException** **Answer: Option D** **154 Which of these method of HashSet class is used to add elements to its object?** **A. add()** **B. Add()** **C. addFirst()** **D. insert()** **Answer: Option A** **155 What will be the output of the following Java program?\ ** **import java.util.\*;** **class Array** **{** **public static void main(String args\[\])** **{** **int array\[\] = new int \[5\];** **for (int i = 5; i \> 0; i\--)** **array\[5 - i\] = i;** **Arrays.sort(array);** **System.out.print(Arrays.binarySearch(array, 4));** **}** **}** **A. 2** **B. 3** **C. 4** **D. 5** **Answer: Option B** **156 What will be the output of the following Java program?\ ** **class Output** **{** **public static void main(String args\[\])** **{** **ArrayList obj = new ArrayList();** **obj.add(\"A\");** **obj.add(\"D\");** **obj.ensureCapacity(3);** **obj.trimToSize();** **System.out.println(obj.size());** **}** **}** **A. 1** **B. 2** **C. 3** **D. 4** **Answer: Option B** **157 Which of this interface must contain a unique element?** **A. Set** **B. List** **C. Array** **D. Collection** **Answer: Option A** **158 What is the difference between length() and size() of ArrayList?** **A. length() and size() return the same value** **B. length() is not defined in ArrayList** **C. size() is not defined in ArrayList** **D. length() returns the capacity of ArrayList and size() returns the actual number of elements stored in the list** **Answer: Option D** **159 If the size of the array used to implement a circular queue is MAX\_SIZE. How rear moves to traverse inorder to insert an element in the queue?** **A. rear=(rear%1)+MAX\_SIZE** **B. rear=(rear+1)%MAX\_SIZE** **C. rear=rear+(1%MAX\_SIZE)** **D. rear=rear%(MAX\_SIZE+1)** **Answer: Option B** **160 What will be the output of the following Java program?\ ** **import java.util.\*;** **class Collection\_iterators** **{** **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);** **Collections.shuffle(list);** **i.next();** **i.remove();** **while(i.hasNext())** **System.out.print(i.next() + \" \");** **}** **}** **A. 2 8 5** **B. 2 1 8** **C. 2 5 8** **D. 8 5 1** **Answer: Option B** **PriorityQueue is thread safe.** **A. True** **B. False** **Answer: Option A** **161 Which of these method is used to make a bit zero specified by the index?** **A. put()** **B. set()** **C. remove()** **D. clear()** **Answer: Option D** **162 Which of these is a method of class Date which is used to search whether object contains a date before the specified date?** **A. after()** **B. contains()** **C. before()** **D. compareTo()** **Answer: Option C** **163 Which of these is a class which uses String as a key to store the value in object?** **A. Array** **B. ArrayList** **C. Dictionary** **D. Properties** **Answer: Option D** **164 When two threads access the same ArrayList object what is the outcome of the program?** **A. Both are able to access the object** **B. ConcurrentModificationException is thrown** **C. One thread is able to access the object and second thread gets Null Pointer exception** **D. One thread is able to access the object and second thread will wait till control is passed to the second one** **Answer: Option B** **165 1What will be the output of the following Java program?\ ** **import java.util.\*;** **class Output** **{** **public static void main(String args\[\])** **{** **ArrayList obj = new ArrayList();** **obj.add(\"A\");** **obj.add(0, \"B\");** **System.out.println(obj.size());** **}** **}** **A. 0** **B. 1** **C. 2** **D. Any Garbage Value** **Answer: Option C** **166 Which data structure is used in Breadth First Traversal of a graph?** **A. Stack** **B. Queue** **C. Array** **D. Tree** **Answer: Option B** **167 Which of these classes is not part of Java\'s collection framework?** **A. Maps** **B. Array** **C. Stack** **D. Queue** **Answer: Option A** MCQ on Packages **168. What is a package in Java?** - a\) A collection of classes - b\) A collection of interfaces - c\) A collection of classes and interfaces - d\) A method of error handling\ **Answer**: c) A collection of classes and interfaces **169. Which keyword is used to define a package in Java?** - a\) import - b\) package - c\) namespace - d\) module\ **Answer**: b) package **170. What is the purpose of a package in Java?** - a\) To organize classes and interfaces - b\) To provide access control - c\) To avoid name conflicts - d\) All of the above\ **Answer**: d) All of the above **171. How do you import a package in Java?** - a\) include packageName; - b\) using packageName; - c\) import packageName; - d\) use packageName;\ **Answer**: c) import packageName; **172. Can a package contain sub-packages in Java?** - a\) Yes - b\) No\ **Answer**: a) Yes **173. Which package is automatically imported in all Java programs?** - a\) java.util - b\) java.io - c\) java.lang - d\) java.math\ **Answer**: c) java.lang **174. How do you import all classes of a package?** - a\) import packageName; - b\) import packageName.\*; - c\) use packageName.\*; - d\) include packageName.all;\ **Answer**: b) import packageName.\*; **175. What is the fully qualified name of a class?** - a\) The class name only - b\) The package name followed by the class name - c\) The import statement - d\) None of the above\ **Answer**: b) The package name followed by the class name **176. Which package contains the Scanner class?** - a\) java.io - b\) java.util - c\) java.lang - d\) java.net\ **Answer**: b) java.util **177. Which package contains classes for input and output operations?** - a\) java.io - b\) java.util - c\) java.lang - d\) java.math\ **Answer**: a) java.io **178. What is the syntax to create a package in Java?** - a\) package packageName; - b\) create package packageName; - c\) namespace packageName; - d\) module packageName;\ **Answer**: a) package packageName; **179. Can two packages have classes with the same name?** - a\) Yes - b\) No\ **Answer**: a) Yes **180. Which of the following is not part of the Java standard library?** - a\) java.util - b\) java.io - c\) java.graphics - d\) java.lang\ **Answer**: c) java.graphics **181. How do you use a class from another package without importing it?** - a\) Use the class name directly - b\) Use the fully qualified name of the class - c\) Use the import keyword - d\) You cannot use it\ **Answer**: b) Use the fully qualified name of the class **182. What is the java.sql package used for?** - a\) Handling math operations - b\) Handling database operations - c\) Handling file operations - d\) Handling networking\ **Answer**: b) Handling database operations **183. Can a package have private classes?** - a\) Yes - b\) No\ **Answer**: a) Yes **184. What is the use of CLASSPATH in Java?** - a\) It specifies the directory for Java libraries - b\) It specifies the location of compiled class files - c\) It specifies the location of package files - d\) All of the above\ **Answer**: d) All of the above **185. Which package contains classes for networking in Java?** - a\) java.util - b\) java.io - c\) java.net - d\) java.nio\ **Answer**: c) java.net **186. What is the use of the java.util package?** - a\) It contains utility classes like Scanner and ArrayList - b\) It is used for mathematical operations - c\) It provides input and output functionality - d\) It is for database connectivity\ **Answer**: a) It contains utility classes like Scanner and ArrayList Multithreading MCQ **187. Which method is used to start a thread in Java?** - a\) run() - b\) execute() - c\) start() - d\) begin()\ **Answer**: c) start() **188. What is the default priority of a thread in Java?** - a\) 0 - b\) 1 - c\) 5 - d\) 10\ **Answer**: c) 5 **189. Which interface must a class implement to create a thread?** - a\) Cloneable - b\) Runnable - c\) Serializable - d\) Comparable\ **Answer**: b) Runnable **190. Which of these is not a state of a thread?** - a\) Running - b\) Waiting - c\) Blocked - d\) Ready **Answer**: c) Blocked **191. How can we stop a thread in Java?** - a\) By using the stop() method (deprecated) - b\) By calling the thread\'s destroy() method - c\) By using System.exit() - d\) None of the above\ **Answer**: a) By using the stop() method (deprecated) **192. Which of these methods is used to make a thread wait until it is notified?** - a\) sleep() - b\) join() - c\) wait() - d\) notify()\ **Answer**: c) wait() **193. What will happen if we call the run() method directly instead of start()?** - a\) A new thread will be created - b\) It will throw an exception - c\) The code will run in the current thread - d\) It will execute parallelly\ **Answer**: c) The code will run in the current thread **194. What does the synchronized keyword do in Java?** - a\) Allows multiple threads to access a method at once - b\) Prevents thread interference and memory consistency errors - c\) Speeds up thread execution - d\) Stops all threads\ **Answer**: b) Prevents thread interference and memory consistency errors **195. Which class is used to create a thread by extending it?** - a\) Thread - b\) Runnable - c\) Executor - d\) Future\ **Answer**: a) Thread **196. What happens if a thread goes to sleep by calling Thread.sleep()?** - a\) The thread releases all locks - b\) The thread releases CPU but holds any locks it has - c\) The thread remains running - d\) The thread stops permanently\ **Answer**: b) The thread releases CPU but holds any locks it has **197. How do you force one thread to wait for another thread to finish in Java?** - a\) join() - b\) sleep() - c\) notify() - d\) wait()\ **Answer**: a) join() **198. Which method checks whether a thread is alive?** - a\) isActive() - b\) isRunning() - c\) isAlive() - d\) isWorking()\ **Answer**: c) isAlive() **199. What is the purpose of the yield() method in Java threads?** - a\) It stops the thread permanently - b\) It pauses the thread to allow other threads of the same priority to execute - c\) It terminates the thread - d\) It resumes a paused thread\ **Answer**: b) It pauses the thread to allow other threads of the same priority to execute **200. Which exception is thrown if the sleep() method is interrupted?** - a\) RuntimeException - b\) InterruptedException - c\) IllegalThreadStateException - d\) None of the above\ **Answer**: b) InterruptedException **201. What does the notifyAll() method do?** - a\) Notifies all waiting threads but only one can acquire the lock - b\) Wakes up all threads waiting on the object\'s monitor - c\) Stops all running threads - d\) Resumes the current thread\ **Answer**: b) Wakes up all threads waiting on the object\'s monitor **202. Which of the following is used to create a thread pool in Java?** - a\) Executors - b\) Runnable - c\) Thread - d\) Callable\ **Answer**: a) Executors **203. What is the main advantage of using thread pools?** - a\) Faster thread creation - b\) Better thread control and resource management - c\) Reduced code complexity - d\) Avoids deadlocks automatically\ **Answer**: b) Better thread control and resource management **204. What is a daemon thread in Java?** - a\) A thread with high priority - b\) A thread running in the background for supporting tasks - c\) A thread created using new Thread() - d\) A thread that cannot be stopped\ **Answer**: b) A thread running in the background for supporting tasks **205. Which method is used to check if the current thread is a daemon thread?** - a\) isDaemon() - b\) isAlive() - c\) isRunning() - d\) isThread()\ **Answer**: a) isDaemon() **206. Which class in Java supports the concept of a monitor?** - a\) Thread - b\) Object - c\) Runnable - d\) Executors\ **Answer**: b) Object