Question regarding to Desert Island Playlist Project

Hi! I got some trouble while trying to complete the project

Here is my code

`import java. util.ArrayList;

class Playlist {
  
  public static void main(String[] args) {
    ArrayList <String> desertIslandPlaylist = new ArrayList <String>(); 
    desertIslandPlaylist.add("A");
    desertIslandPlaylist.add("B");
    desertIslandPlaylist.add("C");
    desertIslandPlaylist.add("D");
    desertIslandPlaylist.add("E");
    desertIslandPlaylist.add("QWE");
    desertIslandPlaylist.remove(3);
    int NumA = desertIslandPlaylist.indexOf("C");
    int NumB = desertIslandPlaylist.indexof("QWE");
    String tempA = desertIslandPlaylist.get(2);
    desertIslandPlaylist.set(NumA , "QWE");
    System.out.println(desertIslandPlaylist);`

I am stuck at Step 10, I try to print out the Arraylist but nothing shows up
I try to type javac Playlist.java to see what is going on and I got this error message

Playlist.java:15: error: cannot find symbol
    int NumB = desertIslandPlaylist.indexof("QWE");
                                   ^
  symbol:   method indexof(String)
  location: variable desertIslandPlaylist of type ArrayList<String>
1 error

I am not quite sure how to fix it
Best

I got it is indexOf…the O is not capitalized