Questions and Answers
What is the Java collection framework used for?
The Java collections framework gives the programmer access to prepackaged data structures as well as to algorithms for manipulating them.
What is a collection?
A collection is an object that can hold references to other objects.
The classes and interfaces of the collections framework are in which package?
java.util
What are the static methods of class Arrays used for?
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What does Arrays method asList return?
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What does method size do?
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What does method get do?
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What is the root interface in the collection hierarchy?
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What does class Collections provide?
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What is a List?
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Which classes implement the Interface List?
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What does Iterator method hasNext do?
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What does method subList return?
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What does method clear do?
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What does method toArray do?
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What does class Vector manage?
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What does Vector method add do?
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What does method insertElementAt do?
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What does Vector method remove do?
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What does method removeAllElements do?
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What does Vector method firstElement do?
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What does Vector method contains do?
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What does Vector method isEmpty do?
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What does algorithm reverse do?
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What does algorithm sort do?
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What does algorithm addAll do?
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Study Notes
Java Collections Framework
- Provides prepackaged data structures and algorithms for manipulating them.
- Located in the
java.util
package.
Collections Definition
- A collection is an object that holds references to other objects.
- Collection interfaces specify operations for each collection type.
Array Manipulation
- Static methods in Class Arrays:
sort
,binarySearch
,equals
, andfill
for array manipulation. -
Arrays.asList
creates a List view of an array, allowing bidirectional changes between the array and the List.
List Interface
- A List is an ordered collection that allows duplicate elements.
- Implemented by classes such as
ArrayList
,LinkedList
, andVector
.
Collection Interface
- The root interface in the collection hierarchy, gives rise to interfaces
Set
andList
. - Includes bulk operations like adding, clearing, and retaining objects, along with an
iterator
method.
Collections Class
- Provides static methods for collection manipulation, implementing polymorphic algorithms for searching and sorting.
Iterator Method
-
hasNext
checks if a collection contains another element. -
next
retrieves and advances to the next object in the collection.
List Modifications
-
clear
removes elements from a List. -
subList
provides a view of a portion of a List, where changes reflect in the original List. -
toArray
converts a collection into an array format.
Vector Class
- Manages dynamically resizable arrays with a default capacity of 10 elements.
- When growing, it either increments by a specified capacity or doubles its size if none is given.
- Methods include
add
for appending elements,remove
for deleting occurrences, andremoveAllElements
for clearing the entire Vector.
Vector Specific Methods
-
firstElement
andlastElement
return references to the first and last elements, respectively. -
contains
checks if a specified searchKey is present. -
indexOf
retrieves the index of the first occurrence of an element, returning -1 if not found. -
isEmpty
determines if the Vector has any elements.
Algorithms
-
reverse
changes the order of List elements. -
fill
alters all elements of a List to a specified object. -
copy
transfers elements from one List to another. -
sort
organizes the List elements in order. -
addAll
appends elements from an array to a collection, whilefrequency
counts occurrences of specified elements in a collection.
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Description
Explore the essential concepts of the Java Collections Framework, including the collection interfaces, array manipulation methods, and the List interface. This quiz will test your knowledge on how these components interact and their significance in Java programming.