从输入读取行到arraylist java

Question

I'm trying to read lines from user's input into arraylist.

Scanner scan = new Scanner(System.in);
    ArrayList<String> lines = new ArrayList<String>();
    while (true) {
        if (scan.nextLine().equals("")) {
            break;
        }
        for (String s : lines) {
            lines.add(scan.nextLine());
        }
    }

    for (int i = 0; i < lines.size(); i++) {
        System.out.println(lines.get(i));
    }

The problem is that last for loop doesnt run. I dont quite understand why break in while loop stops not only while loop.

Answer 1

I dont know why you used for (String s : lines) loop. In your code scan.nextLine() called twice . So it may skip alternative values. Also lines doesn't have any value, so for (String s : lines) condition not allow any values to insert. So only it doesn't display value.

Try this code

        Scanner scan = new Scanner(System.in);
        ArrayList<String> lines = new ArrayList<String>();
        String s;
        while (true) {
            s = scan.nextLine();
            if (s.equals("")) {
                break;
            }
            lines.add(s);
        }

        for (int i = 0; i < lines.size(); i++) {
            System.out.println(lines.get(i));
        }

Answer 2

Here use following code

Scanner scan = new Scanner(System.in);
    ArrayList<String> lines = new ArrayList<String>();
    String s=null;
    while (true) {
        s=scan.nextLine();
        if (s.equals("")) {
            break;
        }else{
            lines.add(s);
        }
    }

    for (int i = 0; i < lines.size(); i++) {
        System.out.println(lines.get(i));
    }