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Questions and Answers
Which method removes all the elements from an invoking collection?
Which method removes all the elements from an invoking collection?
What type of Set does Collections.emptySet() return?
What type of Set does Collections.emptySet() return?
What will be the output of the following Java code snippet? 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);
What will be the output of the following Java code snippet? 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);
What is the initial capacity of the Vector object created with Vector obj = new Vector(4,2); before elements are added?
What is the initial capacity of the Vector object created with Vector obj = new Vector(4,2); before elements are added?
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Which of these structures is responsible for storing associations between keys and values?
Which of these structures is responsible for storing associations between keys and values?
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What will be the output of the following Java program involving a LinkedList and Collections.reverse()?
What will be the output of the following Java program involving a LinkedList and Collections.reverse()?
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Which method is used to search for an element in a list?
Which method is used to search for an element in a list?
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How can an object be removed from an ArrayList?
How can an object be removed from an ArrayList?
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Which of the following options best describes the TreeMap functionality?
Which of the following options best describes the TreeMap functionality?
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When using a Vector with an initial capacity of 4 and increment of 2, what will be its capacity after adding 5 elements?
When using a Vector with an initial capacity of 4 and increment of 2, what will be its capacity after adding 5 elements?
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What is the expected output when executing the Java program that declares an int array and assigns values using a for loop?
What is the expected output when executing the Java program that declares an int array and assigns values using a for loop?
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What will the size of the ArrayList be after adding two elements and calling trimToSize?
What will the size of the ArrayList be after adding two elements and calling trimToSize?
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Which interface ensures that all elements stored are unique when implementing a data structure?
Which interface ensures that all elements stored are unique when implementing a data structure?
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What is the correct distinction between the methods length() and size() when used with an ArrayList?
What is the correct distinction between the methods length() and size() when used with an ArrayList?
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How does the rear pointer of a circular queue update when inserting an element if its size is defined by MAX_SIZE?
How does the rear pointer of a circular queue update when inserting an element if its size is defined by MAX_SIZE?
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What is the expected output of the Java program that uses a LinkedList and performs actions such as reverse, shuffle, and remove?
What is the expected output of the Java program that uses a LinkedList and performs actions such as reverse, shuffle, and remove?
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Which method would be incorrectly defined if applied to an ArrayList?
Which method would be incorrectly defined if applied to an ArrayList?
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In the context of Java collections, which characteristic does not apply to the List interface?
In the context of Java collections, which characteristic does not apply to the List interface?
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What happens to the original order of a LinkedList when the Collections.reverse() method is called?
What happens to the original order of a LinkedList when the Collections.reverse() method is called?
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What will be the value of an array element at index 3 after the completion of a for loop filling a 5-element array with decreasing values from 5?
What will be the value of an array element at index 3 after the completion of a for loop filling a 5-element array with decreasing values from 5?
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What is the output of the following Java program when attempting to access an uninitialized array? import java.util.*; class Array { public static void main(String args[]) { int array[] = new int; 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]); } }
What is the output of the following Java program when attempting to access an uninitialized array? import java.util.*; class Array { public static void main(String args[]) { int array[] = new int; 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]); } }
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Which method is used to remove a specific element from a LinkedList object?
Which method is used to remove a specific element from a LinkedList object?
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What is the expected output of the following program? 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()); } }
What is the expected output of the following program? 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()); } }
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Which of these options accurately describes the relationship between TreeSet and SortedSet?
Which of these options accurately describes the relationship between TreeSet and SortedSet?
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Given the following Java program, what will be the output? 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); } }
Given the following Java program, what will be the output? 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); } }
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What will be the output of the following code with respect to Vector? 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); } }
What will be the output of the following code with respect to Vector? 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); } }
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Which option correctly identifies a class that implements the Set interface?
Which option correctly identifies a class that implements the Set interface?
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Which method will successfully add an element to the beginning of a LinkedList?
Which method will successfully add an element to the beginning of a LinkedList?
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What does the method hasNext() accomplish when used with iterators?
What does the method hasNext() accomplish when used with iterators?
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Study Notes
Java Collection Framework Methods and Concepts
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clear(): Deletes all elements from a collection. -
Collections.emptySet(): Returns an immutable empty Set. -
TreeMap: Sorts elements based on their natural ordering. -
Vector: A dynamic array that can grow or shrink.-
Vector(int initialCapacity, int capacityIncrement): Creates aVectorwith a specified initial capacity and capacity increment. -
capacity(): Returns the current capacity of theVector.Example in the code shows a capacity of 4.
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Map: Stores key-value associations. -
LinkedList: A doubly linked list, allowing efficient insertion and deletion at any point.-
iterator(): Returns an iterator over the elements of theLinkedList. -
Collections.reverse(list): Reverses the order of elements in theLinkedList. -
Collections.shuffle(list): Randomly shuffles the order of elements in theLinkedList.
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ArrayList: A dynamic array that resizes as needed.-
add(): Adds an element to theArrayList. -
ensureCapacity(int minCapacity): Increases the capacity of theArrayListif necessary but doesn't add any element. -
size(): Returns the number of elements in the list. -
trimToSize(): Reduces the capacity of theArrayListto match its actual size.
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Arrays.sort(array): Sorts an array ofint.-
Arrays.binarySearch(array, value): Performs a binary search for a specifiedvaluein a sorted array.
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Iterator: An object that allows traversal of elements in a collection.-
hasNext(): Checks if there are more elements to traverse. -
next(): Retrieves the next element. -
remove(): Removes the last element returned bynext().
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LinkedList.removeFirst(): Removes and returns the first element from theLinkedList. -
LinkedList.removeLast(): Removes and returns the last element from theLinkedList. -
LinkedList.addFirst(): Adds an element to the start of theLinkedList. -
LinkedList.set(index, element): Replaces the element at the specified index. -
Vector.removeAll(Vector): Removes all elements that are present in the specifiedVectorfrom the original one. -
Vector.insertElementAt(obj, index): Inserts an element at a specificindexwithin theVector. -
Hashtable: A class that implements theMapinterface, synchronised by default. -
HashSet.add(): Adds an element to aHashSet. -
Properties: A subclass ofHashtabledesigned to store properties.-
keySet(): Returns aSetview of the keys contained in thePropertiesobject.
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BitSet: A specialized class for storing bits (boolean values).-
get(index): Retrieves a bit at a specificindexfrom theBitSet.
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Collection: An interface that provides methods for manipulating collections in general. -
SortedSet: An interface imposing an ordering on a set,TreeSetis one of its implementations.-
TreeSet: A concrete class implementingSortedSetand storing elements sorted based on their natural order or a custom comparator. -
SortedSetis an interface whereasTreeSetis a concrete class.
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remove(): Removes a specific element in the ArrayList. -
ObjectNotFoundException: Generic exception,IllegalStateExceptionis a specific exception related to invalid iterator operations.
Exception Handling in Collections
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IllegalStateException: Can be thrown by theremove()method of an iterator if thenext()method hasn't been called or if theremovemethod has already been called since the last call tonext().
Specific collection type details
- HashSet: Stores unique elements, no order is guaranteed.
- ArrayList: Ordered collection, elements are accessed using indexes, allows duplicates.
- LinkedList: Ordered collection, elements are linked, provides efficient insertion and deletion at specific positions.
- HashMap / Hashtable: Associative arrays, stores key-value pairs.
- TreeMap: Ordered collection of keys and values. Sorts keys.
Summary of Key Methods
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find(): This method isn't available in the standard Java Collections Framework for searching. UsebinarySearchfor sorted lists or iterate for general search. -
get(): Used to access elements by index inListimplementations (e.g.,ArrayList). -
binarySearch(): Performs a binary search on a sorted array or list. -
fill(): Used to set all elements of a list to the same value. -
next(): Moves to the next element in an iterator. -
add(): Used for adding elements to lists.remove()is for deleting elements.
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Description
Test your knowledge of the Java Collection Framework methods and concepts. This quiz covers essential functionalities such as clear(), TreeMap, Vector, and various collection types like Map and LinkedList. Perfect for anyone looking to solidify their understanding of Java collections.
