Question: I want to write an `ArrayList<String>` into a text file. 

The `ArrayList` is created with the code:

```
ArrayList arr = new ArrayList();

StringTokenizer st = new StringTokenizer(
    line, ":Mode set - Out of Service In Service");

while(st.hasMoreTokens()){
    arr.add(st.nextToken());    
}

```

Answer: 
```
import java.io.FileWriter;
...
FileWriter writer = new FileWriter("output.txt"); 
for(String str: arr) {
  writer.write(str + System.lineSeparator());
}
writer.close();

```
If you want to serialize the ArrayList object to a file so you can read it back in again later use ObjectOuputStream/ObjectInputStream writeObject()/readObject() since ArrayList implements [Serializable](http://download.oracle.com/javase/1.4.2/docs/api/java/io/Serializable.html). It's not clear to me from your question if you want to do this or just write each individual item. If so then Andrey's answer will do that.