How to parse a String in Java without using .parse()?

Question

I'm trying to write a program that will take a string and parse it into two outputs, with the delimiter being a comma. It loops until the user enters the character "q".

i.e.: Console prompts to enter an input, and user inputs "first, second" and then "q" for the second prompt, and the output will be:

Enter input string:
First word: first
Second word: second

Enter input string:

If there is no comma in the input, it throws an error and prompts again

i.e. User inputs "first second" and the output will be:

Enter input string:
Error: No comma in string
Enter input string:

Below is what I have so far:

import java.util.Scanner;

public class ParseStrings {
   public static void main(String[] args) {
         Scanner scnr = new Scanner(System.in); // Scanner for standard input
         Scanner inSS = null;                   // Scanner to write input to buffer
         String firstWord = "";                 // First word string
         String secondWord = "";                // Second word string
         String userInput = "";                 // Input from prompt
         int i = 0;                             // Loop iterator
         boolean inputDone = false;             // Boolean to repeat while loop
         boolean hasComma = false;              // Boolean to check for comma

         // Do while inputDone is false
         while (!inputDone) {

            //Prompt user to input a string
            System.out.println("Enter input string: ");

            // Write string to userInput
            userInput = scnr.nextLine();

            // Exit program if user inputs q
            if((userInput.equals("q"))) {
               inputDone = true;
               break;
            }
            else{

               // Write userInput to buffer
               inSS = new Scanner(userInput);

               // Write first word from buffer
               firstWord = inSS.next();

               // Loop through first word string
               for (i = 0; i < firstWord.length(); ++i) {

                  // If char is a comma, write everything after to secondWord and set inputDone to true
                  if(firstWord.charAt(i) == ',') {
                     secondWord = inSS.next();
                     hasComma = true;
                  }
               }

               // If hasComma is false, return error
               if (!hasComma){
                  System.out.println("Error: No comma in string");
               }
               // Else print first word and second word
               else {
                  System.out.println("First word: " + firstWord);
                  System.out.println("Second word: " + secondWord);
                  System.out.println("");
                  System.out.println("");
               }
            }
         }
        return;
       }
    }

Problems:

• I don't know how to remove the comma from the output
• If there is no space it errors out
• If there is a space between the first word and the comma, it writes firstWord but does not overwrite the previous value for secondWord (or errors if it's the first input given)
• I'm taking a beginner's Java course and we have not gone over the .parse() method yet, so it's not really an option at this time.

Thank you in advance!

Answer 1

Try using string split.

String str="first, second";
String[] arr=str.split(",");
if(arr.length == 2) {
    System.out.println("First :" + arr[0]);
    System.out.println("Second :" + arr[1]);
} if(arr.length > 2) {
    System.out.println("More than 1 comma used.");
} else {
    System.out.println("Error. No comma found.");
}

You can use trim() in case your string has any spaces around comma.

Answer 2

So what I've done is probably the laziest and the most rookie way, but it does work.

Use a for loop to check each character of the string for the comma.

char ch;
String str = "";

if(userInput.charAt(userInput.length()-1) == ',')
    System.out.println("Error. You must have a comma here.");
else {
for(int i = 0; i < userInput.length(); i++)
{
    ch = userInput.charAt(i);
    if(ch != ',')
        str += ch;
    else
    {
        firstWord = str;
        secondWord = userInput.substring(i+1);
        break;
    }
}
}

If the selected letter is not a comma, it is added to the temporary string.

If it is a comma, then the temporary string becomes the first word, and the second word is the string after the occurrence of the comma.

if(userInput.charAt(userInput.length()-1) == ',') Handles the exception that may arise if the input is hello ,, or anything that ENDS with a comma.