ArrayList中的一行没有打印出来

Question

My code has to read 50 lines of input and output them in reverse order, then other 50 lines, so output starts from 50th line, goes to the 1st one, then it start from 100th line to 50th I got it to work. But the only thing, that 51 line isn't printed, I can't get what's going wrong.

public static void doIt(BufferedReader r, PrintWriter w) throws IOException {
    String newString;
    LinkedList<String> list = new LinkedList<String>();
    int i = 0;
    while ((newString = r.readLine()) != null) {
        if (i < 50) {
            i++;
            list.addFirst(newString);
        } else {
            for (String s : list)
                w.println(s);
            list.clear();
            i = 0;
        }
    }

    for (String s : list)
        w.println(s);

}

Answer 1

Change your code as follow:

 i++; 
list.addFirst(newString); 

to

list.addFirst(newString); 
 i++; 

Because the way you are adding newString to list will skip one count

Update:

Sorry but I have to fix my answer rather than deleting this. I checked it twice and as per the right answer add this line :-)

list.addFirst(newString);

Answer 2

You are discarding the line you read when i == 50, here is a fix that makes it work.

public static void doIt(BufferedReader r, PrintWriter w) throws IOException {

String newString;
LinkedList<String> list = new LinkedList<String>();
int i = 0;
while ((newString = r.readLine()) != null) {
    if (i < 50) {
        i++;
        list.addFirst(newString);
    } else {
        for (String s : list)
            w.println(s);
        list.clear();
        list.addFirst(newString); // <---- add this line and you should be fine
        i = 0;
    }
}

for (String s : list)
    w.println(s);

}