user input using while loop to store data

Question

Can you please tell me what is wrong with the following java code.

I am trying to collect input from the user through Scanner class object then store it in an array by using while but it would be infinite loop if i don't supply a break condition , so i thought to break when the input equals "q", but it didn't work.

import java.util.*;
public class ProjectOne{
    public static void main (String []arg){
        ArrayList  one = new ArrayList();
        Scanner input = new Scanner(System.in);
        System.out.println("Enter");
        String x = input.next();       
        while ( input.hasNext()){
           if (x !="q"){
              one.add(input);
           }
           if (x == "q")
           {
              break;
           }
           System.out.println(one);
        }
    }

}

what is wrong with the following java code: it's unreadable because there are 4 empty lines between each line, and the code is not indented. Don't post the question until it looks perfect in the preview. — JB Nizet
– JB Nizet, Commented Apr 15, 2017 at 15:19
See my update answer. I think that is what you are looking for. — strash
– strash, Commented Apr 15, 2017 at 15:49

dumbPotato21 · Accepted Answer · 2017-04-15 15:21:24Z

1

You don't compare String with ==. Use .equals() like

if (!x.equals("q")){

and

if (x.equals("q"))

Note : I think that you aren't using Scanner correctly. You take the input, but keep checking x, instead of the input.

answered Apr 15, 2017 at 15:21

dumbPotato21

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Comments

haMzox · Accepted Answer · 2017-04-15 15:20:55Z

0

Do not compare strings like x =="q"
USE .equals function in java for string comparison. Replace your code with: x.equals("q") for x =="q" and !x.equals("q") for x !="q"

answered Apr 15, 2017 at 15:20

haMzox

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Comments

Vikas Sachdeva · Accepted Answer · 2017-04-15 15:21:07Z

0

You are not reading updated value from Scanner. Below is updated code for your reference after correcting formatting and other errors. Also, instead of == sign, use equals() method for string comparison -

import java.util.*;

public class ProjectOne{ 

public static void main (String []arg ){

    ArrayList one = new ArrayList();
    Scanner input = new Scanner(System.in);
    System.out.println("Enter");
    String x = null;
    while ( input.hasNext()) {
      x = input.next();
      if (!x.equals("q")) {
          one.add(x);
      }
      if (x.equals("q")){
          break;
      }
  }
      System.out.println(one);
}

answered Apr 15, 2017 at 15:21

Vikas Sachdeva

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Comments

strash · Accepted Answer · 2017-04-15 15:48:07Z

0

Scanner reads everything before your ENTER - the whole line you input.

I think that is what you need:

import java.util.ArrayList;
import java.util.Scanner;

public class ProjectOne

{ public static void main (String []arg ){
    ArrayList  one = new ArrayList();
    Scanner input = new Scanner(System.in);
    System.out.println("Enter");
    String pattern;
    String x = input.next();
    while (true){
        String line = input.next();
        if(line.contains("q"))break;
        else{
            x = x + " " + line;
            }
    }
    System.out.println(x);
}

edited Apr 15, 2017 at 15:48

answered Apr 15, 2017 at 15:30

strash

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