Discussion

Questions from previous class

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• Project Status
• Github code repository

Sets And Maps

Learning objectives

• To store unordered,non duplicate element using set
• Explore HashSet,LinkedHashSet,TreeSet
• Understand Map

Sets

• Sets are collections of distinct elements. There are no duplicates. It allows null elements
• Set is an interface.It is abstract data type
• You can create a set using one of its three concrete classes
• HashSet, LinkedHashSet, or TreeSet
• A set is an unordered collection
• Github code Sets

List VS Set

HashSet

• Initial capacity will increase based on data default capacity is 16
• Does not allow duplicate elements
• Allow only one null values
• It is not order
• Elements are stored basis of hashcode
• Best choice to perform search operation
• Github code HashSet

LinkedHashSet

• LinkedHashSet class implements Set interface and extends the HashSet class
• Does not allow duplicate values
• Allow only one null object
• It is Ordered collection
• It's not Synchronized multiple thread can access concurrently.Modification made by one thread will impact other thread
• Github code LinkedHashSet

Treeset

• Stores unique values
• Maintain elements in ascending order
• Elements are stored in sorted order
• It's not Synchronized multiple thread can access concurrently.Modification made by one thread will impact other thread
• Only allow object of the same type
• Allow null values till java 6
• Github code Treeset

Hashset VS LinkedHashSet VS TreeSet

Map

• A map stores association between keys and values.
• Each key links to exactly on value from a key value pair known as entry.
• Retrieving values by key is fast
• Does not extend Collection interface
• MAP Key (K),Value(v)
• Github code Map

Map Methods

• Map is similar to dictionary. It has word and at least one definition.
• V put(K key,V value)
• Creates a new map entry for the provided key-value pair, if it does not exist
• If key exists the old value is overwritten
• Returns null if the map does not contain key
• V get(Object key)
• Returns null if the map does not contain key
• Removes the map entry fo the provided key
• V remove(Object key)
• Github code Map

HashMap

• Hash table based implementation of the Map interface
• This will not preserve the order in which these data were inserted.
• Store items in "key/value" pairs
• Github code HashMap

LinkedHashMap

• Java LinkedHashMap contains values based on the key.
• Java LinkedHashMap contains unique elements.
• Java LinkedHashMap maintains insertion order.
• K: It is the type of keys maintained by this map.
• V: It is the type of mapped values.
• Github code LinkedHashMap

TreeMap

• It provides an efficient means of storing key-value pairs in sorted order.
• Java TreeMap cannot have a null key but can have multiple null values.
• Java TreeMap maintains ascending order.
• K: It is the type of keys maintained by this map.
• V: It is the type of mapped values.
• Github code TreeMap

Java Docs

• Java Docs Guidelines
• Sample code

                        
                        part 1 : description 
                        part 2 : tag list
                        How to run javadoc
                        cmd line: javadoc -d doc src* or javadoc -d doc src* -author -version
                        From Intellij = Tools => Generate javaDocs => select Whole project => ok
                        
                        

Thank you