JAVA Scanner should read from console every single character and save it in a Stack

Question

my code is never closing my Scanner input stream. It let's me type in stuff in the console but does not close it with enter.

    public Stack<String> einlesen(){
    Scanner sc = new Scanner(System.in);
    Stack<String> st = new Stack<>();
    //String zeichen;
    System.out.println("Bitte geben Sie einen Text ein: ");
    while (sc.hasNext()) {
        st.push(sc.next());
    }
    //sc.close();
    return st;
}

Edit:

How can I achieve, that I can type text in the console and when I hit the Enter key, it jumps back from console to my code? Like the readline() function.

Edit2:

Ok since it doesn't seem to be possible that easy with the scanner class. I will try it with the DataInputStream Class. I will try something like: first write some text in console, write that whole thing into a variable and then go through every single character in that variable. Thanks for your help though.

@Cappuccino90 *Hmm could the condition be a stroke of the "Enter" key?* Sure. Remove the while loop. — Elliott Frisch, Aug 27 '14 at 00:53
don't you need to specify the type of the Stack in Java? something like Stack st = new Stack(); — Josh Engelsma, Aug 27 '14 at 00:54
First `zeichen` is not declared or initialized. And second, write your code in English, we don't read German... — Nir Alfasi, Aug 27 '14 at 00:55
@JoshEngelsma That is the [diamond operator](http://stackoverflow.com/q/4166966/2970947). — Elliott Frisch, Aug 27 '14 at 00:55
Also, as @alfasin said...your zeichen is never given a type, or initialized before you push it — Josh Engelsma, Aug 27 '14 at 00:56
I edited my original post a bit. Forgot a few things that I had in my code though. Still doesn't work. — Quatsch, Aug 27 '14 at 00:59
You still never assign anything to zeichen before you push it the first time — Josh Engelsma, Aug 27 '14 at 01:00
@Cappuccino90 **Why** do you want to save one line into a `Stack`? — Elliott Frisch, Aug 27 '14 at 01:07
I want to write a mirror application. It reads your text, and writes it in the opposite order. And I want to do that with a stack, because I never worked with stack before. — Quatsch, Aug 27 '14 at 01:09
@Cappuccino90 `StringBuilder` has a [`reverse()`](http://docs.oracle.com/javase/7/docs/api/java/lang/StringBuilder.html#reverse%28%29) method. — Elliott Frisch, Aug 27 '14 at 01:09
That is a very interesting thing :) Very helpful. But I really want to try the Stack thingy out. The reverse function would be kinda cheating in my case haha — Quatsch, Aug 27 '14 at 01:13

Elliott Frisch · Accepted Answer · 2014-08-27T01:15:52.047

I believe this

String zeichen;
System.out.println("Bitte geben Sie einen Text ein: ");
while (sc.hasNext()) {
  st.push(zeichen);
  zeichen = sc.next();
}

Should be something like -

// String zeichen;
System.out.println("Bitte geben Sie einen Text ein: ");
if (sc.hasNextLine()) { // <--- while to get multiple lines. if for one line.
   String str = sc.nextLine();
  // if (str.equalsIgnoreCase("quit")) { // <-- possibly, if you want multiple
  //                                     // lines.
  //   break;
  // }
  st.push(str);
}

Edit

Based on your comments, and edits - I think you really wanted a Stack<Character> (not String),

public Stack<Character> einlesen(){
    Scanner sc = new Scanner(System.in);
    Stack<Character> st = new Stack<>();
    System.out.println("Bitte geben Sie einen Text ein: ");
    if (sc.hasNextLine()) {
        String str = sc.nextLine();
        for (char ch : str.toCharArray()) {
            st.push(ch);
        }
    }
    return st;
}

It is not the perfect solution for my problem but that might also have been the fault of my english skills. Thanks a lot Elliott Frisch. — Quatsch, Aug 27 '14 at 01:22

JAVA Scanner should read from console every single character and save it in a Stack

1 Answers1