What is List interface in java

The List interface is a sub interface of Collection under java.util package . it’s index stars from zero (0) . The diagram represents, List interface and it’s implementations .

List interface List is an ordered collection , it allows both duplicates and null elements .

List interface we can search elements by index .

List interface It is not a synchronized collection , Use Collections.synchronizedList(List list)for synchronized List .

All methods of List interface :

Syntax:

List ‹generic type› ‹object name›= new <List implemented class name>‹generic type›(); or

Example for List interface :

import java.util.List;
import java.util.ArrayList;
class ListExample 
{
	public static void main(String[] args) 
	{
		List<Object> listVal = new ArrayList<object>();
		  listVal.add("Cat");
		  listVal.add("Dog");
		  listVal.add("Mouse");
		  listVal.add("Donkey");
		System.out.println("List elements are :"+listVal);

		//get(int) method
		System.out.println("Get by index :"+listVal.get(2));

		//indexOf(Object) method returns int
		System.out.println("Index of the element :"+listVal.indexOf("Dog"));

		//isEmpty() returns boolean
		System.out.println("isEmpty() :"+listVal.isEmpty());

		//lastIndexOf() returns int
		System.out.println("lastIndex of element :"+listVal.lastIndexOf("Donkey"));

		//set(int,element) method
		listVal.set(3,"Hen");
		System.out.println("After replace element :"+listVal);

		//size() method returns int
		System.out.println("Size of the List :"+listVal.size());

		//subList(int,int) method returns List
		List subList = listVal.subList(1,3);
		System.out.println("SubList :"+subList);

		//remove(index or element) method 
		listVal.remove(2);
		System.out.println("After removed :"+listVal);
	}
}

import java.util.List;

import java.util.ArrayList;

class ListExample

{

public static void main(String[] args)

{

List<Object> listVal = new ArrayList<object>();

listVal.add("Cat");

listVal.add("Dog");

listVal.add("Mouse");

listVal.add("Donkey");

System.out.println("List elements are :"+listVal);

//get(int) method

System.out.println("Get by index :"+listVal.get(2));

//indexOf(Object) method returns int

System.out.println("Index of the element :"+listVal.indexOf("Dog"));

//isEmpty() returns boolean

System.out.println("isEmpty() :"+listVal.isEmpty());

//lastIndexOf() returns int

System.out.println("lastIndex of element :"+listVal.lastIndexOf("Donkey"));

//set(int,element) method

listVal.set(3,"Hen");

System.out.println("After replace element :"+listVal);

//size() method returns int

System.out.println("Size of the List :"+listVal.size());

//subList(int,int) method returns List

List subList = listVal.subList(1,3);

System.out.println("SubList :"+subList);

//remove(index or element) method

listVal.remove(2);

System.out.println("After removed :"+listVal);

}

List elements are :[Cat, Dog, Mouse, Donkey]
Get by index :Mouse
Index of the element :1
isEmpty() :false
lastIndex of element :3
After replace element :[Cat, Dog, Mouse, Hen]
Size of the List :4
SubList :[Dog, Mouse]
After removed :[Cat, Dog, Hen]

List elements are :[Cat, Dog, Mouse, Donkey]

Get by index :Mouse

Index of the element :1

isEmpty() :false

lastIndex of element :3

After replace element :[Cat, Dog, Mouse, Hen]

Size of the List :4

SubList :[Dog, Mouse]

After removed :[Cat, Dog, Hen]

Few more methods :

Method Name	Returns	Description
addAll(Collection)	Boolean	To add Collection of elements ( if they are not present).
containsAll(Collection)	Boolean	Returns true , if the List having all elements.
iterator()	Iterator	To iterate List .
removeAll(Collection)	boolean	To Remove specified Collection of elements .
retainAll(Collection)	boolean	To Keep specified Collection of elements .
toArray()	Object[]	It returns an array with all elements .
toArray(T[] t)	T[]	It returns specified array(ex:String[]) ,with all elements .
listIterator()	ListIterator	To iterate List .

List interface Some of the List implementations prohibits to add null elements .

What is an interface and how to work with an interface in java

What is the difference between interface and abstract class in java

What is Map interface in java

What is Set interface in java

Difference between List and Set

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