Vector listIterator() method in Java with Examples
This method returns a list iterator over the elements of a Vector object in proper sequence. It is bidirectional, so both forward and backward traversal is possible, using next() and previous() respectively. The iterator thus returned is fail-fast. This means that structurally modifying the vector after the iterator is created, in any way except through the iterator’s own remove or add methods (using Vector.add(), for example), will cause iterator to throw ConcurrentModificationException.
Syntax:
public ListIterator listIterator()
Parameters: This method accepts no input arguments.
Return Value: This method returns a ListIterator object which can be used to traverse the Vector object.
Example 1: To demonstrate forward and backward traversal using listIterator().
// Java code to illustrate listIterator() import java.util.Vector; import java.util.ListIterator; public class GFG { public static void main(String[] args) { // Declare empty vector Vector<String> vt = new Vector<String>(); vt.add("Geeks"); vt.add("for"); vt.add("Geeks"); vt.add("2019"); vt.add("AComputerSciencePortalForGeeks"); // Declare list iterator ListIterator listItr = vt.listIterator(); // Forward iterations System.out.println("Forward Traversal:"); while (listItr.hasNext()) { System.out.println(listItr.next()); } // Backward iterations System.out.println("\nBackward Traversal:"); while (listItr.hasPrevious()) { System.out.println(listItr.previous()); } } } |
Forward Traversal: Geeks for Geeks 2019 AComputerSciencePortalForGeeks Backward Traversal: AComputerSciencePortalForGeeks 2019 Geeks for Geeks
This method is used to return a list iterator by specifying starting index. Also bidirectional and fail-fast.
Syntax:
public ListIterator listIterator(int index)
Parameters: The parameter index is an integer type value that specifies the first element to be returned from the list iterator (by a call to next()).
Return Value: This method returns a ListIterator object which can be used to traverse the Vector object.
Exception: This method throws IndexOutOfBoundsException, if the index is out of range (index < 0 or index > size())
Example 2: To demonstrate listIterator(int index).
// Java code to illustrate listIterator(int index) import java.util.Vector; import java.util.ListIterator; public class GFG { public static void main(String[] args) { // Declare empty vector Vector<String> vt = new Vector<String>(); vt.add("Geeks"); vt.add("for"); vt.add("Geeks"); // Declare list iterator ListIterator listItr = vt.listIterator(1); // traversal while (listItr.hasNext()) { System.out.println(listItr.next()); } } } |
for Geeks
Example 3: To demonstrate IndexOutOfBoundsException thrown by listIterator(int index).
// Java code to illustrate IndexOutOfBoundsException // thrown by listIterator(int index) import java.util.Vector; import java.util.ListIterator; public class GFG { public static void main(String[] args) { // Declare empty vector Vector<String> vt = new Vector<String>(); vt.add("Geeks"); vt.add("for"); vt.add("Geeks"); // Declare list iterator at starting // index greater than vector size try { ListIterator listItr = vt.listIterator(5); } catch (IndexOutOfBoundsException e) { // Exception handling System.out.println("Exception: " + e); } } } |
Exception: java.lang.IndexOutOfBoundsException: Index: 5
Example 4: To demonstrate ConcurrentModificationException thrown by ListIterator object when Vector object is modified after creating list iterator to it.
// Java code to illustrate ConcurrentModificationException // thrown by ListIterator object import java.util.ConcurrentModificationException; import java.util.Vector; import java.util.ListIterator; public class GFG { public static void main(String[] args) { // Declare empty vector Vector<String> vt = new Vector<String>(); vt.add("Geeks"); vt.add("for"); // Declare list iterator ListIterator listItr = vt.listIterator(); // modify vector after creating list iterator vt.add("Geeks"); try { // Exception thrown here System.out.println(listItr.next()); } catch (ConcurrentModificationException e) { // Exception handling System.out.println("Exception: " + e); } } } |
Exception: java.util.ConcurrentModificationException
Reference:
https://docs.oracle.com/javase/8/docs/api/java/util/Vector.html#listIterator–
