Abstract List in Java

In Java, the Abstract List is the part of the Java Collection Framework. The Abstract list is implemented by the collection interface and the Abstract Collection class. This is used when the list can not be modified. To implement this AbstractList class is used with get() and size() methods.

Below is the class Hierarchy

Syntax:

	
public abstract class AbstractList<E> extends AbstractCollection<E>implements List<E>
	

Below are the methods of AbstractList Class

Example:

	
import java.util.*; 

public class AbstractListDemo1 { 
    public static void main(String args[]) 
    { 
AbstractList list = new LinkedList(); 
list.add("Dog"); 
list.add("Cat"); 
list.add("Bird"); 
list.add("Tiger"); 
list.add("Rabit"); 

	System.out.println("***********************************");
System.out.println("Elements in the List 1:" + list);

	list.add(3, "Deer"); 
	System.out.println("***********************************************************"); 
System.out.println("After Adding Deer at position 3");

	System.out.println("Elements in the List 1:" + list); //New List
	System.out.println("***********************************************************");
	AbstractList list1 = new LinkedList();
	list1.add("Dog"); 
        list1.add("Cat"); 
        list1.add("Bird"); 
        list1.add("Tiger"); 
        list1.add("Rabit"); 
	System.out.println("***********************************************************");
System.out.println("Elements in the List 2 :" + list1); //New List2
	System.out.println("***********************************************************");
	boolean ab = list.equals(list1); 
	System.out.println("Are both list equal : "+ ab); 
	System.out.println("***********************************************************");	
	String bc = list1.get(3);
	System.out.println("Get element of index 3 : "+bc);
	System.out.println("***********************************************************");
	int cd= list.hashCode();
System.out.println("HashCode : " + cd); 
	System.out.println("***********************************************************");
	int de= list.indexOf("Bird"); 
	System.out.println("index of Bird in List 1: " + de); 
	System.out.println("***********************************************************");
	Iterator ef = list.iterator(); 
            while (ef.hasNext()) 
		{ 
System.out.println("Element : "+ ef.next()); 
		}
	System.out.println("***********************************************************");
	intfg= list.lastIndexOf("Rabit"); 
	System.out.println("Last index of Rabit : "+ fg); 
	System.out.println("***********************************************************");
	ListIteratorgh = list.listIterator(3); 
System.out.println("The list is as follows:"); 
        while (gh.hasNext()) { 
System.out.println(gh.next()); 
        } 
	System.out.println("***********************************************************");
    } 
}
	

Immutable List

In Java, Immutable List is immutable. The Elements of the Immutable list are Fixed. It means the elements of the list are read-only. If we try to add, delete or update any element then it will throw UnsupportedOperationException. It also does not allow null elements. If we try to create a null element then it will throw NullPointerException and if we try to add null element then it will throw UnsupportedOperationException.

Following are the Advantages of the ImmutableList.

1. It is threaded safe.

2. The memory is well organized.

Below is the class Hierarchy