CopyOnWriteArrayList listIterator() method in Java

The listIterator() method of CopyOnWriteArrayList returns an listIterator over the elements in this list in proper sequence. The listIterator does NOT support the remove, set or add methods.

Syntax: 

public ListIterator listIterator()

Parameters: The function does not accept any parameters.

Return Value: The function returns a list iterator over the elements in this list (in proper sequence)

Below programs illustrate the above function:

Program 1:

Java

// Java Program to illustrate the CopyOnWriteArrayList
// listIterator() method in Java
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.*;

public class GFG {
    public static void main(String[] args)
    {

        // create object of CopyOnWriteArrayList
        CopyOnWriteArrayList<Integer> ArrLis
            = new CopyOnWriteArrayList<Integer>();

        // Add elements
        ArrLis.add(32);
        ArrLis.add(67);
        ArrLis.add(67);
        ArrLis.add(100);

        // print CopyOnWriteArrayList
        System.out.println("CopyOnWriteArrayList: " + ArrLis);

        // Call listIterator() method of
        Iterator iteratorVals = ArrLis.listIterator();

        // Print elements of iterator
        // created from CopyOnWriteArrayList
        System.out.println("The iterator values"
                           + " of CopyOnWriteArrayList are:");

        // prints the elements using an iterator
        while (iteratorVals.hasNext()) {
            System.out.println(iteratorVals.next());
        }
    }
}

Output:

CopyOnWriteArrayList: [32, 67, 67, 100]
The iterator values of CopyOnWriteArrayList are:
32
67
67
100

The listIterator(index) method of CopyOnWriteArrayList returns an listIterator over the elements in this list in proper sequence starting from a particular index. The listIterator does NOT support the remove, set or add methods.

Syntax: 

public ListIterator listIterator(int index)

Parameters: The function accepts a parameter index which specifies the index of the first element to be returned from the list iterator.

Return Value: The function returns a list iterator over the elements in this list starting from the specified index (in proper sequence).

Exceptions: The function throws IndexOutOfBoundsException if the index is out of range.

Below programs illustrate the above function:

Program 1: 

Java

// Java Program to illustrate the CopyOnWriteArrayList
// listIterator() method in Java
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.*;

public class GFG {
    public static void main(String[] args)
    {

        // create object of CopyOnWriteArrayList
        CopyOnWriteArrayList<String> ArrLis
            = new CopyOnWriteArrayList<String>();

        // Add elements
        ArrLis.add("gopal");
        ArrLis.add("gfg");
        ArrLis.add("jgec");
        ArrLis.add("sudo");

        // print CopyOnWriteArrayList
        System.out.println("CopyOnWriteArrayList: " + ArrLis);

        // Call listIterator() method from 2nd index
        Iterator iteratorVals = ArrLis.listIterator(2);

        // Print elements of iterator
        // created from CopyOnWriteArrayList
        System.out.println("The iterator values"
                           + " of CopyOnWriteArrayList are:");

        // prints the elements using an iterator
        while (iteratorVals.hasNext()) {
            System.out.println(iteratorVals.next());
        }
    }
}

Output:

CopyOnWriteArrayList: [gopal, gfg, jgec, sudo]
The iterator values of CopyOnWriteArrayList are:
jgec
sudo

Program 2: 

Java

// Java Program to illustrate the CopyOnWriteArrayList
// listIterator() method in Java, exception
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.*;

public class GFG {
    public static void main(String[] args)
    {

        // create object of CopyOnWriteArrayList
        CopyOnWriteArrayList<String> ArrLis
            = new CopyOnWriteArrayList<String>();

        // Add elements
        ArrLis.add("gopal");
        ArrLis.add("gfg");
        ArrLis.add("jgec");
        ArrLis.add("sudo");

        // print CopyOnWriteArrayList
        System.out.println("CopyOnWriteArrayList: " + ArrLis);

        // Call listIterator() method from 6th index
        // hence exception is returned
        Iterator iteratorVals = ArrLis.listIterator(6);

        // Print elements of iterator
        // created from CopyOnWriteArrayList
        System.out.println("The iterator values"
                           + " of CopyOnWriteArrayList are:");

        // prints the elements using an iterator
        while (iteratorVals.hasNext()) {
            System.out.println(iteratorVals.next());
        }
    }
}

Output:

Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 6
    at java.util.concurrent.CopyOnWriteArrayList.listIterator(CopyOnWriteArrayList.java:1107)
    at GFG.main(GFG.java:25)

Reference: https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/CopyOnWriteArrayList.html#listIterator–