element 0: Amy element 1: Bob element 2: Cindy element 0: Zoe element 1: Bob element 2: Cindy
You can insert an element at a specific index from 0
to size()
.
The newly added element is now located at the specified index, and the indexes of all
elements above that element is increased by one.
If you add an element at index size()
, the element is appended to the end of the list.
void add(int index, E elt) // Inserts the element atindex
. Each element with // an index greater thanindex
is shifted upward // and now has an index one greater than its previous value.
The method throws an
IndexOutOfBoundsException
if the index is out of bounds,
either negative or greater than size()
.
This prevents you from creating a list with gaps between elements.
The following program uses this method:
import java.util.* ; public class ArrayListEgFour { public static void main ( String[] args) { ArrayList<String> names = new ArrayList<String>(); names.add( "Amy" ); names.add( "Bob" ); names.add( "Chris" ); // Print original arrangement System.out.println("Before adding at index 1:"); for ( int j=0; j < names.size(); j++ ) System.out.println( j + ": " + names.get(j) ); // Insert an element names.add( 1, "Valerie"); // Print new arrangement System.out.println("\nAfter adding at index 1:"); for ( int j=0; j < names.size(); j++ ) System.out.println( j + ": " + names.get(j) ); } }
The program prints out:
Before adding at index 1: 0: Amy 1: Bob 2: Chris After adding at index 1: 0: Amy 1: Valerie 2: Bob 3: Chris
Would the following statement work in the above program?
names.add(5, "Gertrude");