How to replace existing value of ArrayList element in Java [duplicate]

Question

I am still quite new to Java programming and I am trying to update an existing value of an ArrayList by using this code:

public static void main(String[] args) {

    List<String> list = new ArrayList<String>();

    list.add( "Zero" );
    list.add( "One" );
    list.add( "Two" );
    list.add( "Three" );

    list.add( 2, "New" ); // add at 2nd index

    System.out.println(list);
}

I want to print New instead of Two but I got [Zero, One, New, Two, Three] as the result, and I still have Two. I want to print [Zero, One, New, Three]. How can I do this? Thank You.

Answer 1

Use the set method to replace the old value with a new one.

list.set( 2, "New" );

Answer 2

If you are unaware of the position to replace, use list iterator to find and replace element ListIterator.set(E e)

ListIterator<String> iterator = list.listIterator();
while (iterator.hasNext()) {
     String next = iterator.next();
     if (next.equals("Two")) {
         //Replace element
         iterator.set("New");
     }
 }

Answer 3

Use ArrayList.set

list.set(2, "New");

Answer 4

You must use

list.remove(indexYouWantToReplace);

first.

Your elements will become like this. [zero, one, three]

then add this

list.add(indexYouWantedToReplace, newElement)

Your elements will become like this. [zero, one, new, three]