trouble using .useDelimiter

[Sebastion Hill]

Hi I am trying to use scanner to accept user input. I would like for the user to enter in 3 sets of numbers in the date format mm/dd/yr. I thought that by using "reader.useDelimiter("/");" that I could get each integer seperated by the "/" sign.

Could someone help me out, first with my logic and then with general syntax? :-) My thinking is obviously wrong but I don't know if I use .nextInt to get the first integer value AND THEN use the delimiter for the remaining two or if it should just work regardless of when I insert the .useDelimiter

    
             Scanner reader = new Scanner(System.in)

             int activityMonth = 0;
             int activityDay = 0;
             int activityYear = 0;
             int activityHour = 0;
             int activityMinute = 0;

             System.out.print("Please enter the due date for this activity (use the MM/DD/YR format): ");
             //reader.useDelimiter("/");
             try {
             activityMonth = reader.nextInt() - 1;
             System.out.println("Made it past month");
             activityDay = reader.nextInt();
             System.out.println("Made it past Day");
             activityYear = reader.nextInt();
             System.out.println("Made it past Year"); 
             } catch (InputMismatchException ex) {
             System.exit(1);
             }

[Jason Irwin]

The problem you're having is with Scanner(System.in).

Imagine the user types in "12/07/09". You then ask the Scanner to chop that up using "/". You think you should get "12", "07", "09" but you don't. The Scanner knows it got an input stream, so it can't be sure if "9" is the end or if something more is going to come; so it sits and waits. If you type in "/", the Scanner will then see another token, but it will see "09\n/" and you'll get an exception.

There's a few ways to solve this, and how really depends on the requirements (I assume this is for a project or something). I'll try and give you a few clues. What is the total user input for the date? "12/07/09" and what else?
Can you use that in your delimiter? Is there a way to make the Scanner "see" that at the end and not wait for more?

[pete stein]

the delimiter is a regex. I think that you can split with "/" but you also need to split on white space so that it can swallow the end of line character. Perhaps something like

reader.useDelimiter("[/\\s]");

A better solution is to use a SimpleDateFormat formatter, and appropriate format string and parse your input String to date.

e.g.,

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Scanner;

public class Fu4 {
  public static void main(String[] args) {

    Scanner reader = new Scanner(System.in);

    System.out.print("Please enter the due date(use the MM/DD/YR format): ");
    //reader.useDelimiter("[/\\s]");
    String input = reader.nextLine();

    // another way to do this is to split the input String
    String[] tokens = input.split("/");
    for (String token : tokens) {
      System.out.println(token);
    }

    // but this is likely the best way to do this
    SimpleDateFormat sdf = new SimpleDateFormat("MM/dd/yyyy");
    try {
      Date date = sdf.parse(input);
      System.out.println(date);
    } catch (ParseException e) {
      e.printStackTrace();
    }

  }
}

[Sebastion Hill]

Jason Irwin wrote:The problem you're having is with Scanner(System.in).

Imagine the user types in "12/07/09". You then ask the Scanner to chop that up using "/". You think you should get "12", "07", "09" but you don't. The Scanner knows it got an input stream, so it can't be sure if "9" is the end or if something more is going to come; so it sits and waits. If you type in "/", the Scanner will then see another token, but it will see "09\n/" and you'll get an exception.

There's a few ways to solve this, and how really depends on the requirements (I assume this is for a project or something). I'll try and give you a few clues. What is the total user input for the date? "12/07/09" and what else?
Can you use that in your delimiter? Is there a way to make the Scanner "see" that at the end and not wait for more?

Hey Jason and Pete, thanks so much for your feedback. I am trying to digest it all right now but I did want to write back before getting back to the actual code.

Jason - I THINK I know what you're getting at ... if I know that the date is going to be a specific format then I should set up the scanner so that it doesn't just look for "/" but rather looks for the whole "##/##/##\n"???

Also, I am trying to write an Android program for cell phones, a time management program (aka a planner), and I need to learn Java first. So I am taking it in baby steps and this is where I get a due date for when an activity needs to be completed :-) Thanks so much though, on to read pete's comments now

[Sebastion Hill]

pete stein wrote:the delimiter is a regex. I think that you can split with "/" but you also need to split on white space so that it can swallow the end of line character. Perhaps something like

reader.useDelimiter("[/\\s]");

A better solution is to use a SimpleDateFormat formatter, and appropriate format string and parse your input String to date.

e.g.,

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Scanner;

public class Fu4 {
  public static void main(String[] args) {

    Scanner reader = new Scanner(System.in);

    System.out.print("Please enter the due date(use the MM/DD/YR format): ");
    //reader.useDelimiter("[/\\s]");
    String input = reader.nextLine();

    // another way to do this is to split the input String
    String[] tokens = input.split("/");
    for (String token : tokens) {
      System.out.println(token);
    }

    // but this is likely the best way to do this
    SimpleDateFormat sdf = new SimpleDateFormat("MM/dd/yyyy");
    try {
      Date date = sdf.parse(input);
      System.out.println(date);
    } catch (ParseException e) {
      e.printStackTrace();
    }

  }
}

Oh wow, I REALLY like the SimpleDateFormat Pete! Thanks a million. I added the Hour and Minutes as well since my next question would have been how do you add time. Now I need to figure out how to take the Date and use it in the Calendar format ... though I am wondering if I even need the calendar format now.

I have one more question in regards to scanner. I am inserting my code below (it looks gross, I am sorry) and I was wondering why I had to implement a new scanner called dateReader (Line 48). I originally tried using reader from earlier but it would always skip my input ... I figure it has something to do with my try catch statements (lines 20 & 34) but I don't know why. Could someone explain ... again, please forgive the sloppy coding, still new :-)

   
      public void prompt() {
             //prompt user for input choice
             String activityName;
             String activityDescription;
             int activityImportanceNumber = 0;
             int activityUrgencyNumber = 0;
             boolean activityImportance = false;
             boolean activityUrgency = false;
             
             Scanner reader = new Scanner(System.in);      

             System.out.println("");
             System.out.print("Please enter activity name: "); // Display the string
             activityName = reader.nextLine();
             System.out.print("Please enter activity description: "); // Display the string
             activityDescription = reader.nextLine();

             System.out.print("Enter '1' if this activity is 'Important' or enter '2' if it is not: ");
             try {
             activityImportanceNumber = reader.nextInt();
             } catch (InputMismatchException ex) {
                     System.out.println("You have to enter in a NUMBER aka an integer, not a string!");
                     System.out.println("Start over and try again.");
                     prompt();
             }
             switch (activityImportanceNumber) {
                    case 1: activityImportance = true; break;
                    case 2: activityImportance = false; break;
                    default: System.out.println("You must enter either a 1 or 2"); System.out.println("Start Over"); prompt();
             }

             System.out.print("Enter '1' if this activity is 'Urgent' or enter '2' if it is not: ");
             try {
             activityUrgencyNumber = reader.nextInt();
             } catch (InputMismatchException ex) {
                     System.out.println("You have to enter in a NUMBER aka an integer, not a string!");
                     System.out.println("Start over and try again.");
                     prompt();
             }
             switch (activityUrgencyNumber) {
                    case 1: activityUrgency = true; break;
                    case 2: activityUrgency = false; break;
                    default: System.out.println("You must enter either a 1 or 2"); System.out.println("Start Over"); prompt();
             }

             //trying it the forum way
             Scanner dateReader = new Scanner(System.in);
             System.out.print("Please enter the due date(use the MM/DD/YR/HH/mm format): ");  
             String dateLine = dateReader.nextLine();

             SimpleDateFormat sdf = new SimpleDateFormat("MM/dd/yyyy/HH/mm");
             try {
                 Date date = sdf.parse(dateLine);
                 System.out.println(date);
             } catch (ParseException e) {
                 e.printStackTrace();
             }

             
             //trying to use the Calendar class
             //Calendar dueDate = Calendar.getInstance();
             
             //int activityMonth = 0;
             //int activityDay = 0;
             //int activityYear = 0;
             //int activityHour = 0;
             //int activityMinute = 0;

             //System.out.print("Please enter the due date for this activity (use the MM/DD/YR format): ");
             //reader.useDelimiter("/");
             //try {
             //activityMonth = reader.nextInt() - 1;
             //System.out.println("Made it past month");
             //activityDay = reader.nextInt();
             //System.out.println("Made it past Day");
             //activityYear = reader.nextInt();
             //System.out.println("Made it past Year"); 
             //} catch (InputMismatchException ex) {
             //System.exit(1);
             //}
             //System.out.print("Please enter a time between 00:00 - 23:59 for when this activity is due: ");
             //reader.useDelimiter(":");
             //activityHour = reader.nextInt();
             //activityMinute = reader.nextInt();             

             //dueDate.set(activityYear, activityMonth, activityDay, activityHour, activityMinute);
             
             //System.out.println("This activity is due on: " + dueDate.getTime());

             //need to take the info from above and create a new activity object 
             Activity testActivity = new Activity();
             testActivity.setActivityName(activityName);
             testActivity.setActivityDescription(activityDescription);
             testActivity.setActivityImportance(activityImportance);
             testActivity.setActivityUrgency(activityUrgency);
             testActivity.setPriorityCode(activityImportance, activityUrgency);
             System.out.println("Made it past creating a new activity object!");    

             //put the activity object into an arraylist of activity objects based on priority level
             int pCode = testActivity.getPriorityCode();
             switch (pCode) {
                    case 3: Priority1.add(testActivity); System.out.println("Passed into Priority1 array"); break;             
                    case 4: Priority2.add(testActivity); System.out.println("Passed into Priority2 array"); break;
                    case 5: Priority3.add(testActivity); System.out.println("Passed into Priority3 array"); break;
                    case 6: Priority4.add(testActivity); System.out.println("Passed into Priority4 array"); break; 
                    default: System.out.println("You did something wrong!"); break;
             }
            
             //call checkActivityArray method
             checkActivityArray();
             System.out.println("Made it past the call checkActivityArray");
      }

[Sebastion Hill]

again sorry if some of the println statements don't make sense ... i use it as debugging almost, to see if I make it to that line or not when running my code ... so I might just be talking to myself in some of the code :-/

[pete stein]

My guess for why you are needing to use a second Scanner is that the first one is stuck at an end of line, that you need to call

reader.nextLine();

after reading in all your ints before it will respond to more input. I could be wrong, but I've seen this before.

i.e.,

    //Scanner dateReader = new Scanner(System.in);
    reader.nextLine(); // swallow the end of line character and keep on reading
    System.out.print("Please enter the due date(use the MM/DD/YR/HH/mm format): ");
    //String dateLine = dateReader.nextLine();
    String dateLine = reader.nextLine();

[Sebastion Hill]

thanks Pete, your suggestion worked perfectly! :-) ... I have to put in all my try-statements now but for the most part I think I've completed my very first java program :-D ... thanks to you and the other forum members, thanks again!

[Sebastion Hill]

btw, does anyone know the SPECIFIC import java.?.? statement for Collections.sort(list, comparator)??? I know I can use import java.util.* but I was curious as to what I would type in if it weren't for the *

[Campbell Ritchie]

Different question

import java.util.Collections;

You can be very specific and try

import static java.util.Collections.sort;

but read a tutorial about static import before you try that. A few links: 1 2 3 4. Note that sort method is specifically mentioned in link no 2.

[Rob Spoor]

A static import of java.util.Collections.sort is a bad idea, because there is also java.util.Arrays.sort. If a static method / field is used in more than one often used class I would never even consider static imports.