#92 ArrayList in Java

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In this lecture we will learn:
- Collection in Java
- Use of collection interface and classes
- What is the use of Generics?
- ArrayList and its properties
- How ArrayList is different from Arrays?
- Advantages of Collection framework

#1
- API means a library or some features that we can use directly, we do not need to define an implementation for it.
- Collections List, Queue, Map and Set simply extend the Collection interface and this collection interface must have its own class implementation.
- we can also convert a collection into an array.
- ArrayList is used like:
Collection nums=new ArrayList();
- We can add values in a collection by using the add() method.
-- We do not have indexing for the collection API.
- In the array, we need to specify its type of it. While Collection API works with objects.
- All the data types classes like integer and float extend an object class and thus collection API directly use an object.

#2
- To define the data types in collection API, we use Generics.
- You can define the type of an object to which data type class it belongs in angular brackets like:
Collection(Integer) nums= new ArrayList Integer ();
- Here, we use Integer as it is a class, while int is a primitive data type.
- If we do not specify the datatype of a collection object, then it will give a run-time error.

#3
- ArrayList is a class that implements a list. The list does not have a method called get because it list works with an index in the values.
- It uses a dynamic array to store the duplicate element of different data types.
- The ArrayList class maintains the insertion order and is non-synchronized.
- The elements stored in the ArrayList class can be randomly accessed.
- The size of an ArrayList is increased automatically if the collection grows or shrinks if the objects are removed from the collection.
- If you want to use and fetch values from an ArrayList, then you can use Collection.
Collection Integer nums= new ArrayList Integer ();
- If you want to work with an index value, you should use List as it supports index values.
List Integer nums= new ArrayList Integer ();

#4 Advantages of Collection Framework:
- Consistent API
- Reduces programming efforts
- Increases program speed and quality

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[GodofStories]

Your explanations, and the way you teach has improved a lot since those vids I've seen from 6 years ago. Especially the presentation. Great stuff!

[Gianni.]

hi, I have this error when I write list instead of Collection.
The List type is not generic; cannot be parameterized with <Integer> arguments

How is it possible?

[pavanmudhole]

actually I was watching this video to know about initial capacity and load factor

[muskaanchaudhary]

I have a doubt how did import java.xml.transform.Source ; come like sir I think you didn’t explain about it