Question about heap memory in Java

There was a question about heap memory. So pay attention to the bold italics. in the 1st version, everything works fine. But in the second one, {[3] pops up]}

OutOfMemoryError: Java heap space.

Who can tell you why?

public class idea_test {
    public static void main(String[] args) throws IOException {
        BufferedReader reader = new BufferedReader(new FileReader("S:\\idea test\\src\\file.txt")); 
        ArrayList strings = new ArrayList();  

        (1)          
        String s;                                           
        while ((s = reader.readLine()) != null){
            strings.add(s);                                                     
        }

        (2)
        String s = reader.readLine();                                           
        while (s != null){
            strings.add(s);                                                     
        }

        reader.close();                                                         
        String[] strings1 = strings.toArray(new String[strings.size()]);        
        Arrays.sort(strings1);                                                  
        for (String s1 : strings1) {
            System.out.println(s1);
        }
    }
}