Introduction

In this article, we will learn about cursor in the collection framework. If we want to get objects from the collection one by one, we have to use the cursor. Using the cursor, we can retrieve or traverse the object from the collection one by one. There are three cursors in the collection framework-

  1. Enumeration
  2. Iterator
  3. ListIterator

1. Enumeration Cursor

Enumeration is used to retrieve elements from the collection one by one. We can get an enumeration object by using the elements() method.

How to create an enumeration object?

Enumeration e=v.elements();

Here, v is a Vector class object.

Enumeration Methods

There are two methods,

Example 

import java.util.*;

class abc{
	public static void main(String args[]){
		Vector v=new Vector();
		v.add("Abhishek");
		v.add("Harshit");
		v.add("Shruti");
		v.add("Pranav");
		v.add("Arpit");
		v.add("Ishika");
        //Create enumeration object		
		Enumeration e=v.elements();
	    // apply enumeration methods
		while(e.hasMoreElements()){
			System.out.println(e.nextElement());
		}
	}
}

Output

Enumeration output

Enumeration Limitations

2. Iterator Cursor

The iterator cursor is introduced to overcome the limitation of the enumeration cursor. An iterator is used to retrieve elements from the collection one by one. The iterator is a universal cursor which means it is applicable for all collection classes.

How to create an Iterator object?

Iterator itr=list.iterator();

Here, the list is an ArrayList class object.

Iterator Methods

There are three methods,

Example 

import java.util.*;

class abc{
	
	public static void main(String args[]){
		ArrayList list=new ArrayList();
		list.add("Abhishek");
		list.add("Harshit");
		list.add("Shruti");
		list.add("Pranav");
		list.add("Arpit");
		list.add("Ishika");
		
        //Create iterator object		
		Iterator  itr=list.iterator();
	    // apply Iterator  methods
		while(itr.hasNext()){
			String str=String.valueOf(itr.next());
			if(str.equals("Abhishek")){
				// apply remove method
				itr.remove();
			}
			else{
				System.out.println(str);
			}
		}
		// Updated list
		System.out.println("List:"+list);
	}
}

Output

Iterator Limitations

3. ListIterator Cursor

The listiterator cursor is introduced to overcome the limitation of the iterator cursor. The listiterator is also used to retrieve elements from the collection one by one. The listiterator is a bi-directional cursor which means we can move forward and backward direction.

How to create an Iterator object?

ListIterator itr=list.listIterator();

ListIterator Methods

There are various methods,

Example

import java.util.*;

class abc{
	
	public static void main(String args[]){
		ArrayList list=new ArrayList();
		list.add("Abhishek");
		list.add("Harshit");
		list.add("Shruti");
		list.add("Pranav");
		list.add("Arpit");
		list.add("Ishika");
		
        //Create ListIterator object		
		ListIterator itr=list.listIterator();
	    // ListIterator forward direction methods,remove() and add() method
		
		System.out.println("List is:");
		while(itr.hasNext()){
			String str=String.valueOf(itr.next());
			System.out.println(str);
			if(str.equals("Abhishek")){
				// remove method
				itr.remove();
			}
			else if(str.equals("Pranav")){
				itr.remove();
				// add method
				itr.add("Reena");
			}
		}
		
		// Updated list
		System.out.println("List:"+list);
		
		System.out.println("List is:");
		// ListIterator backward direction methods and add() method
		while(itr.hasPrevious()){
		String str=String.valueOf(itr.previous());
			System.out.println(str);
			if(str.equals("Arpit")){
				// set method
				itr.set("Manu");
			}
		}		
		// Updated list
		System.out.println("List:"+list);			
	}
}

Output

Conclusion

In this article, we have seen how we can use the cursor to retrieve the object from the collection one by one. Thanks for reading and hope you like it. If you have any suggestions or queries on this article, please share your thoughts.