Question

In the code below, sBar is an arraylist. I am trying to convert it to String and then write it to file. However, I don’t know what I did wrong here as I keep getting error message saying:
– NullPointerException
– Exception in thread “Thread-1” java.lang.ClassCastException: java.lang.Long cannot be cast to java.lang.String

try{
   FileWriter writer = new FileWriter("stime.txt");
    for (Iterator it = sBar.iterator(); it.hasNext();) {
        String str = (String) it.next();
        writer.write(str);
     }
    }
 } catch (IOException e) {
 }

Answer 1

You can’t convert a long to a string by casting. Change

String str = (String) it.next();

to

String str = it.next().toString();

---

Another way to write it would be to use a for each loop:

for (Long val : sBar)
    writer.write(String.valueOf(val));