Collections in Java With Examples

The Java Collections Framework is a collection of interfaces and classes which helps in storing and processing the data efficiently. This framework has several useful classes which have tons of useful functions which makes a programmer task super easy. I have written several tutorials on Collections in Java. All the tutorials are shared with examples and source codes to help you understand better.

Java Collections – Table of Contents

1. ArrayList
2. LinkedList
3. Vector
4. HashSet
5. LinkedHashSet
6. TreeSet
7. HashMap
8. TreeMap
9. LinkedHashMap
10. Hashtable
11. Iterator and ListIterator
12. Comparable and Comparator
13. Java Collections Interview Questions

Collections Framework hierarchy

Java Collections – List

A List is an ordered Collection (sometimes called a sequence). Lists may contain duplicate elements. Elements can be inserted or accessed by their position in the list, using a zero-based index.

ArrayList

Here is the list of all the tutorials published on the ArrayList.

ArrayList Basics

ArrayList in Java
Initialize ArrayList
Loop ArrayList
Find length of ArrayList

ArrayList Sorting

Sort ArrayList
Sort ArrayList in Descending order
Sort ArrayList of Objects using Comparable and Comparator

ArrayList Add/Remove

Add element to ArrayList
Add element at particular index of ArrayList
Append Collection elements to ArrayList
Copy All List elements to ArrayList
Insert all the collection elements to the specified position in ArrayList
Remove element from the specified index in ArrayList
Remove specified element from ArrayList

Get/Search in ArrayList

Get Sub List of ArrayList
Get the index of last occurrence of the element in the ArrayList
Get element from ArrayList
Get the index of first occurrence of the element in the ArrayList
Check whether element exists in ArrayList

Other Tutorials on ArrayList

Compare two ArrayList
Synchronize ArrayList
Swap two elements in ArrayList
Override toString() method – ArrayList
Serialize ArrayList
Join two ArrayList
Clone ArrayList to another ArrayList
Make ArrayList Empty
Check whether ArrayList is empty or not
Trim the Size of ArrayList
Replace the value of existing element in ArrayList
Increase the capacity(size) of ArrayList

ArrayList Conversions:

Convert ArrayList to String Array
Convert Array to ArrayList

Differences:

ArrayList vs Vector
ArrayList vs HashMap
ArrayList vs LinkedList

LinkedList

Here is the list of all the tutorials published on the LinkedList.

LinkedList Basics

LinkedList in Java
How to iterate LinkedList

LinkedList Add/Remove

Adding an element to LinkedList
Add element at specific index in LinkedList
Add element at the beginning and end of LinkedList
Adding an element to the front of LinkedList
Remove First and last elements from LinkedList
Remove element from specific index
Remove specified element from LinkedList
Remove All elements from LinkedList
Append all the elements of a List to LinkedList

Get/Search in LinkedList

Get first and last elements from LinkedList
Get element from specific index of LinkedList
Search element in LinkedList
Get Sub list of LinkedList

LinkedList Iterator/ListIterator

LinkedList Iterator example
LinkedList ListIterator example
Iterate a LinkedList in reverse Order

Other Tutorials on LinkedList

Replace element with a new value in LinkedList
Check whether a particular element exists in LinkedList
Clone a LinkedList to another LinkedList
Get the index of last occurrence of an element in LinkedList
LinkedList push() and pop() methods
LinkedList poll(), pollFirst() and pollLast() methods
LinkedList peek(), peekFirst() and peekLast() methods

Conversion

Convert LinkedList to ArrayList
Convert LinkedList to Array

Vector

Here is the list of all the tutorials published on the Vector.

Vector basics

Vector in Java
Get sub list from Vector
Sort Vector using Collections.sort()
Search element in Vector using index
Copy Elements of one Vector to another

Remove/Sort/Replace in Vector

Remove element from Vector
Remove element from specified index in Vector
Remove all elements from Vector
Replace element in Vector
Set Vector size

Vector -Iterator/ListIterator/Enumeration

Vector enumeration example
Vector Iterator example
Vector ListIterator example

Conversions

Convert Vector to List
Convert Vector to ArrayList
Convert Vector to String Array

Java Collections – Set

A Set is a Collection that cannot contain duplicate elements. There are three main implementations of Set interface: HashSet, TreeSet, and LinkedHashSet. HashSet, which stores its elements in a hash table, is the best-performing implementation; however it makes no guarantees concerning the order of iteration. TreeSet, which stores its elements in a red-black tree, orders its elements based on their values; it is substantially slower than HashSet. LinkedHashSet, which is implemented as a hash table with a linked list running through it, orders its elements based on the order in which they were inserted into the set (insertion-order).

HashSet

Here is the list of all the tutorials published on the HashSet.

HashSet in Java
Delete all elements from HashSet
How to iterate through a HashSet
Convert a HashSet to an array
Convert a HashSet to a TreeSet
Convert HashSet to a List/ArrayList
HashSet vs HashMap

LinkedHashSet

LinkedHashSet in Java
List Vs Set

TreeSet

TreeSet in Java
HashSet vs TreeSet

Java Collections – Map

A Map is an object that maps keys to values. A map cannot contain duplicate keys. There are three main implementations of Map interfaces: HashMap, TreeMap, and LinkedHashMap.
HashMap: it makes no guarantees concerning the order of iteration
TreeMap: It stores its elements in a red-black tree, orders its elements based on their values; it is substantially slower than HashMap.
LinkedHashMap: It orders its elements based on the order in which they were inserted into the set (insertion-order).

HashMap

Here is the list of all the tutorials published on the HashMap.

HashMap Basics

HashMap in Java
How to iterate HashMap
Sort HashMap by Keys and values
Get Size of HashMap
Remove Key-value mapping from HashMap
Remove all mapping from HashMap
How to check if HashMap is empty or not?

Get/Search in HashMap

Check if particular key exists in HashMap
Check if particular value exists in HashMap

Serialize/Synchronize

Serialize HashMap
Synchronize HashMap

Differences

HashMap vs Hashtable
HashSet vs HashMap

Other Tutorials on HashMap

HashMap Iterator example
Copy one HashMap to another
Get value from HashMap using Key
Get Set view of keys from HashMap
Clone a HashMap

TreeMap

TreeMap in Java
Iterate TreeMap
Sort TreeMap
Iterate TreeMap in Reverse order
Get Sub Map from TreeMap

LinkedHashMap

LinkedHashMap in Java

Hashtable

Hashtable in Java

Java Collections – Iterator/ListIterator

Both Iterator and ListIterator are used to iterate through elements of a collection class. Using Iterator we can traverse in one direction (forward) while using ListIterator we can traverse the collection class on both the directions(backward and forward). To know more differences between these two refer this article: Difference between Iterator and ListIterator.

Iterator
ListIterator

Comparable and Comparator Interfaces

These interfaces are used for sorting objects of user defined class (custom class).

Comparable interface with example
Comparator interface with example

Collections Interview Questions

Collections Framework Interview Questions

Reference: Official Document on Collections

varneyjoacity.blogspot.com

Source: https://beginnersbook.com/java-collections-tutorials/