Why object of array from file has NumberFormatException in Java?

I need to read a .txt file line by line and store each line to an array. Each array has 3 elements, empId, name, salary, which are fields of SalariedEmployee class. My code has a NumberFormatException, I have no idea which step goes wrong. Any hint or help would be appreciated. Thanks. Please don't close my question, I'm a beginner of Java.

Exception message:

Exception in thread "main" java.lang.NumberFormatException: For input string: "Kelsey"
at java.base/jdk.internal.math.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:2054)
at java.base/jdk.internal.math.FloatingDecimal.parseDouble(FloatingDecimal.java:110)
at java.base/java.lang.Double.parseDouble(Double.java:549)
at com.maoding.Hw3_Part2.main(Hw3_Part2.java:23)

.txt fie:

1, Kelsey, 65000
2, Jake, 89000
3, Carlos, 105000
4, Clarence, 58000
5, Pacheco, 68000
6, Piotr, 120000
7, Adam, 47000
8, Yorst, 77000
9, Silas, 93000
10, Yapsiong, 85000

SalariedEmployee class:

public class SalariedEmployee {
// instance variable
    public int empId;
    public String name;
    public double salary;

// constructor
    public SalariedEmployee(int empId, String name, double salary) {
        this.empId = empId;
        this.name = name;
        this.salary = salary;
}
// get methods
    public int getEmpId() {
        return empId;
}

    public String getName(){
        return name;
}

    public double getSalary(){
        return salary;
}

main class:

public class Hw3_Part2 {
    public static void main(String[] args) throws IOException {
        int empId;
        String name;
        double salary;

        String[] words;
        Scanner fileInput = new Scanner(new File("/Users/hw3_employees.txt"));
        while (fileInput.hasNextLine()) {
            words = fileInput.nextLine().split(",|\\s+");
       
            for (int i = 0; i < words.length; i++) {
                empId = Integer.parseInt(words[0]);
                name = words[1];
                salary = Double.parseDouble(words[2]);
                SalariedEmployee se = new SalariedEmployee(empId, name, salary);
                System.out.println(words);
                System.out.println(se);
            }
    }
}     

The problem is with your regex.

(",|\\s+") - Here you are splitting it if it either encounters a comma or a space. The pipe stands for OR. So, your array is actually greater than size 3.

What you need is to split it on a combination of both comma and space. So, your regex should be (",\\s+"). It needs to be a comma followed by a space.

Your problem is the regular expression in the call to method split().

Rather than just post the answer, I will try to explain the process of debugging. Every programmer needs to learn how to debug his code. You can also refer to How to Debug Small Programs

Because I can't show you, via the capabilities of this site, how to use the debugger in your IDE, I will present an alternative process, namely inserting methods that print to standard output (which is usually the computer screen).

Since the error message is telling you that your program is trying to parse Kelsey as a number, that should indicate that maybe the words array is not what you expect it to be. Hence you need to display the actual value of words. This is what the below code does.

public static void main(String[] args) throws IOException {
    int empId;
    String name;
    double salary;

    String[] words;
    Scanner fileInput = new Scanner(new File("/Users/hw3_employees.txt"));
    while (fileInput.hasNextLine()) {
        words = fileInput.nextLine().split(",|\\s+");
        System.out.println("words.length = " + words.length); // Added this line
        for (int i = 0; i < words.length; i++) {
            System.out.printf("words[0] = ^%s^%n", words[0]); // Added this line
            empId = Integer.parseInt(words[0]);
            name = words[1];
            System.out.printf("words[1] = ^%s^%n", words[1]); // Added this line.
            salary = Double.parseDouble(words[2]);
            System.out.printf("words[2] = ^%s^%n", words[2]); // Added this line.
            SalariedEmployee se = new SalariedEmployee(empId, name, salary);
            System.out.println(words);
            System.out.println(se);
        }
    }
}

This is the output I get when running the above code.

words.length = 5
words[0] = ^1^
words[1] = ^^
Exception in thread "main" java.lang.NumberFormatException: For input string: "Kelsey"
	at java.base/jdk.internal.math.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:2054)
	at java.base/jdk.internal.math.FloatingDecimal.parseDouble(FloatingDecimal.java:110)
	at java.base/java.lang.Double.parseDouble(Double.java:549)

• First of all, I see that words contains five elements and not three.
• I add the ^ symbol to the string that I want to display as it helps me see if there is whitespace in the value. Hence I see that words[1] is an empty string.

At this stage, you should realize that you need to change the regular expression. In order to know what to change it to, look at the javadoc for method split(). It has a link to class java.util.regex.Pattern which explains how the java regular expression engine works. Then try experimenting. Write a separate program. Hard code a string that is one line from your text file and see what results you get for different regular expressions until you find the right one.

For now, I will tell you that one way to solve the problem is simply to split on the comma alone and then trim each "word".

public static void main(String[] args) throws IOException {
    int empId;
    String name;
    double salary;

    String[] words;
    Scanner fileInput = new Scanner(new File("/Users/hw3_employees.txt"));
    while (fileInput.hasNextLine()) {
        words = fileInput.nextLine().split(",");
        System.out.println("words.length = " + words.length);
        for (int i = 0; i < words.length; i++) {
            System.out.printf("words[0] = ^%s^%n", words[0]);
            empId = Integer.parseInt(words[0].trim());
            name = words[1];
            System.out.printf("words[1] = ^%s^%n", words[1]);
            salary = Double.parseDouble(words[2].trim());
            System.out.printf("words[2] = ^%s^%n", words[2]);
            SalariedEmployee se = new SalariedEmployee(empId, name, salary);
            System.out.println(words);
            System.out.println(se);
        }
    }
}

Now the output is.

words.length = 3
words[0] = ^1^
words[1] = ^ Kelsey^
words[2] = ^ 65000^
[Ljava.lang.String;@49c2faae
SalariedEmployee@20ad9418
words[0] = ^1^
words[1] = ^ Kelsey^
words[2] = ^ 65000^
[Ljava.lang.String;@49c2faae
SalariedEmployee@31cefde0
words[0] = ^1^
words[1] = ^ Kelsey^
words[2] = ^ 65000^
[Ljava.lang.String;@49c2faae
SalariedEmployee@439f5b3d
words.length = 3
words[0] = ^2^
words[1] = ^ Jake^
words[2] = ^ 89000^
[Ljava.lang.String;@1d56ce6a
SalariedEmployee@5197848c
words[0] = ^2^
words[1] = ^ Jake^
words[2] = ^ 89000^
[Ljava.lang.String;@1d56ce6a
SalariedEmployee@17f052a3
words[0] = ^2^
words[1] = ^ Jake^
words[2] = ^ 89000^
[Ljava.lang.String;@1d56ce6a
SalariedEmployee@2e0fa5d3
words.length = 3
words[0] = ^3^
words[1] = ^ Carlos^
words[2] = ^ 105000^
[Ljava.lang.String;@5010be6
SalariedEmployee@685f4c2e
words[0] = ^3^
words[1] = ^ Carlos^
words[2] = ^ 105000^
[Ljava.lang.String;@5010be6
SalariedEmployee@7daf6ecc
words[0] = ^3^
words[1] = ^ Carlos^
words[2] = ^ 105000^
[Ljava.lang.String;@5010be6
SalariedEmployee@2e5d6d97
words.length = 3
words[0] = ^4^
words[1] = ^ Clarence^
words[2] = ^ 58000^
[Ljava.lang.String;@238e0d81
SalariedEmployee@31221be2
words[0] = ^4^
words[1] = ^ Clarence^
words[2] = ^ 58000^
[Ljava.lang.String;@238e0d81
SalariedEmployee@377dca04
words[0] = ^4^
words[1] = ^ Clarence^
words[2] = ^ 58000^
[Ljava.lang.String;@238e0d81
SalariedEmployee@728938a9
words.length = 3
words[0] = ^5^
words[1] = ^ Pacheco^
words[2] = ^ 68000^
[Ljava.lang.String;@21b8d17c
SalariedEmployee@6433a2
words[0] = ^5^
words[1] = ^ Pacheco^
words[2] = ^ 68000^
[Ljava.lang.String;@21b8d17c
SalariedEmployee@5910e440
words[0] = ^5^
words[1] = ^ Pacheco^
words[2] = ^ 68000^
[Ljava.lang.String;@21b8d17c
SalariedEmployee@6267c3bb
words.length = 3
words[0] = ^6^
words[1] = ^ Piotr^
words[2] = ^ 120000^
[Ljava.lang.String;@533ddba
SalariedEmployee@246b179d
words[0] = ^6^
words[1] = ^ Piotr^
words[2] = ^ 120000^
[Ljava.lang.String;@533ddba
SalariedEmployee@7a07c5b4
words[0] = ^6^
words[1] = ^ Piotr^
words[2] = ^ 120000^
[Ljava.lang.String;@533ddba
SalariedEmployee@26a1ab54
words.length = 3
words[0] = ^7^
words[1] = ^ Adam^
words[2] = ^ 47000^
[Ljava.lang.String;@3d646c37
SalariedEmployee@41cf53f9
words[0] = ^7^
words[1] = ^ Adam^
words[2] = ^ 47000^
[Ljava.lang.String;@3d646c37
SalariedEmployee@5a10411
words[0] = ^7^
words[1] = ^ Adam^
words[2] = ^ 47000^
[Ljava.lang.String;@3d646c37
SalariedEmployee@2ef1e4fa
words.length = 3
words[0] = ^8^
words[1] = ^ Yorst^
words[2] = ^ 77000^
[Ljava.lang.String;@306a30c7
SalariedEmployee@b81eda8
words[0] = ^8^
words[1] = ^ Yorst^
words[2] = ^ 77000^
[Ljava.lang.String;@306a30c7
SalariedEmployee@68de145
words[0] = ^8^
words[1] = ^ Yorst^
words[2] = ^ 77000^
[Ljava.lang.String;@306a30c7
SalariedEmployee@27fa135a
words.length = 3
words[0] = ^9^
words[1] = ^ Silas^
words[2] = ^ 93000^
[Ljava.lang.String;@46f7f36a
SalariedEmployee@421faab1
words[0] = ^9^
words[1] = ^ Silas^
words[2] = ^ 93000^
[Ljava.lang.String;@46f7f36a
SalariedEmployee@2b71fc7e
words[0] = ^9^
words[1] = ^ Silas^
words[2] = ^ 93000^
[Ljava.lang.String;@46f7f36a
SalariedEmployee@5ce65a89
words.length = 3
words[0] = ^10^
words[1] = ^ Yapsiong^
words[2] = ^ 85000^
[Ljava.lang.String;@25f38edc
SalariedEmployee@1a86f2f1
words[0] = ^10^
words[1] = ^ Yapsiong^
words[2] = ^ 85000^
[Ljava.lang.String;@25f38edc
SalariedEmployee@3eb07fd3
words[0] = ^10^
words[1] = ^ Yapsiong^
words[2] = ^ 85000^
[Ljava.lang.String;@25f38edc
SalariedEmployee@506c589e

Now you can remove the "debug" statements from your code.

Note that if you want a "human readable" string when you print a SalariedEmployee object, you need to override method toString(), but that would be a different question. Feel free to ask another question

The error is the regex pattern,|\\s+. It doesn't match the array size.
I have modified the code to correct this as ,\\s+, and added additional steps so that the code does not print the hashcode of the class instead of the String. Also that for loop is not necessary in the while loop.

Here is the modified code:

class SalariedEmployee {
// instance variable
private int empId;
private String name;
private double salary;
// constructor
public SalariedEmployee(int empId, String name, double salary) {
this.empId = empId;
this.name = name;
this.salary = salary;
}
// get methods
public int getEmpId() {
int e = this.empId
return e;
}
public String getName(){
String n = this.name;
return n;
}
public double getSalary(){
Double sal = this.salary;
return sal;
}
@Override
public String toString(){
String s = this.getEmpId()+","+this.getName()+","+this.getSalary();
return s;
}
}
public class Stacktest{
public static void main(String[] args) throws Exception {
int empId;
String name;
double salary;
String[] words;
Scanner fileInput = new Scanner(new File("File Location here"));
while (fileInput.hasNextLine()) {
words = fileInput.nextLine().split(",\\s+");
//System.out.println(Arrays.toString(words));
empId = Integer.parseInt(words[0]);
name = words[1].toString();
salary = Double.parseDouble(words[2]);
SalariedEmployee se = new SalariedEmployee(empId, name, salary);
System.out.println(Arrays.toString(words));
System.out.println(se.toString());
}
}
}

Generally, when you print objects, toString() is invoked internally. It returns the classname, @ which refers to string and a hashcode of the location. To overcome this, you need to override the existing toString() method and send the actual String value.

Output before toString() overriding

[Ljava.lang.String;@6a5fc7f7
stacktest.SalariedEmployee@3b6eb2ec
[Ljava.lang.String;@1e643faf
stacktest.SalariedEmployee@6e8dacdf
[Ljava.lang.String;@7a79be86
stacktest.SalariedEmployee@34ce8af7
[Ljava.lang.String;@b684286
stacktest.SalariedEmployee@880ec60
[Ljava.lang.String;@3f3afe78
stacktest.SalariedEmployee@7f63425a
[Ljava.lang.String;@36d64342
stacktest.SalariedEmployee@39ba5a14
[Ljava.lang.String;@511baa65
stacktest.SalariedEmployee@340f438e
[Ljava.lang.String;@30c7da1e
stacktest.SalariedEmployee@5b464ce8
[Ljava.lang.String;@57829d67
stacktest.SalariedEmployee@19dfb72a
[Ljava.lang.String;@17c68925
stacktest.SalariedEmployee@7e0ea639

Output after toString() overriding

[1, Kelsey, 65000]
1,Kelsey,65000.0
[2, Jake, 89000]
2,Jake,89000.0
[3, Carlos, 105000]
3,Carlos,105000.0
[4, Clarence, 58000]
4,Clarence,58000.0
[5, Pacheco, 68000]
5,Pacheco,68000.0
[6, Piotr, 120000]
6,Piotr,120000.0
[7, Adam, 47000]
7,Adam,47000.0
[8, Yorst, 77000]
8,Yorst,77000.0
[9, Silas, 93000]
9,Silas,93000.0
[10, Yapsiong, 85000]
10,Yapsiong,85000.0

It is a best practice to set class variables to private and use public getter and setter methods to access those class variables.(I'm saying this because you mentioned you are a beginner in java). I used public getters for the private variables in the code.