“java.lang.NumberFormatException：empty String”，非空字符串

Question

I am currently working on a personal project outside of class and am running into some issues while reading in a text file into a linked list. When reading in the first double I get a

java.lang.NumberFormatException: empty String

error. I added a print line into the program to print out what I am trying to parse into a double and the variable is in fact, not empty, and is in fact a double.

Like I said above, I added a print line to print out the string I am trying to parse into a double and it seems to be okay. Here is the String that is read in and split into the array I am printing from:

500.0 % 04/05/2019 % This is paycheck 1 % true % 49.5

I have to parse two strings into doubles and I only run into problems with the first one. When I comment out the first double being parsed, the program runs with no problems. Here is the full output from running to program

 *File loading*


    *500.0*

    *Exception in thread "main" java.lang.NumberFormatException: empty String*
        *at sun.misc.FloatingDecimal.readJavaFormatString(Unknown Source)*
        *at sun.misc.FloatingDecimal.parseDouble(Unknown Source)*
        *at java.lang.Double.parseDouble(Unknown Source)*
        *at fileHandling.readPaycheck(fileHandling.java:194)*
        *at UserMenu.main(UserMenu.java:20)*

The problems happens in the "Splitting the array into its appropriate temp variables" section in this line of code:

payCheckAmount = Double.parseDouble(tempArray[0]);

Here is the code for the method this is in

public void readPaycheck(LinkedList<PayCheck> paycheck) throws IOException {

        // Declare Variables
        Scanner sc = new Scanner(payChecks); // Scanner used to read in from the payChecks text file
        String temp; // A string used to hold the data read in from the file temporarily
        String[] tempArray; // A String array used to temporarily hold data from the text file
        double payCheckAmount; // A double holding the amount of the paycheck
        String paycheckDate; // A string holding the date of the paycheck
        String description; // A string holding a description of the paycheck
        boolean payCheckSplit; // A boolean stating if the paycheck has been split or not
        double amountUnSplit; // A double

        // A while loop that runs while the text file still has data in it
        while (sc.hasNextLine()) {

            // Reading in a new line from the paycheck file
            temp = sc.nextLine();
            // Splitting the line into an array
            tempArray = temp.split(" % ");

            // Temp output used for testing of the issue at hand
            System.out.println(tempArray[0]);

            // Splitting the array into its appropriate temp variables
            payCheckAmount = Double.parseDouble(tempArray[0]);
            paycheckDate = tempArray[1];
            description = tempArray[2];
            payCheckSplit = Boolean.parseBoolean(tempArray[3]);
            amountUnSplit = Double.parseDouble(tempArray[4]);

            // putting the temp variables into a temp paycheck object
            PayCheck tempCheck = new PayCheck(payCheckAmount, paycheckDate, description, payCheckSplit, amountUnSplit);
            paycheck.add(tempCheck);

        }

    }

Edit:

Here is a Minimal, Complete, and Verifiable example of the problem I am running into:

import java.io.File;
import java.io.IOException;
import java.util.Scanner;

public class test {

    public static void main(String[] args) throws IOException {

        // Declare Variables
        File payChecks = new File("C:\\Users\\zwtw\\Documents\\paychecks.txt");
        Scanner sc = new Scanner(payChecks); 

    while (sc.hasNextLine()) {

            String temp = sc.nextLine();

            String[] tempArray = temp.split(" % ");

            System.out.println(tempArray[0]);

            // Splitting the array into its appropriate temp variables
            double payCheckAmount = Double.parseDouble(tempArray[0]);
            String paycheckDate = tempArray[1];
            String description = tempArray[2];
            boolean payCheckSplit = Boolean.parseBoolean(tempArray[3]);
            double amountUnSplit = Double.parseDouble(tempArray[4]);

        }
    }
}

Here is the content of the text file mentioned in the code above:

500.0 % 04/05/2019 % This is paycheck 1 % true % 49.5
450.0 % 04/09/2019 % This is paycheck 2 % true % 49.75

Answer 1

Your text file likely contains empty lines. You can either remove the new lines in the text file, change how the text file is created, or just skip the empty lines when you read it.

This is how you skip the empty lines:

while (sc.hasNextLine()) {

        String temp = sc.nextLine();

        if (temp.equals("")) { continue; } // <--- notice this line
        String[] tempArray = temp.split(" % ");

        System.out.println(tempArray[0]);

        // Splitting the array into its appropriate temp variables
        double payCheckAmount = Double.parseDouble(tempArray[0]);
        String paycheckDate = tempArray[1];
        String description = tempArray[2];
        boolean payCheckSplit = Boolean.parseBoolean(tempArray[3]);
        double amountUnSplit = Double.parseDouble(tempArray[4]);

    }
}