java.lang.NumberFormatException: 对于输入字符串：""-StringBuilder

Question

The main goal of the program is to sum of extract the dollar amount / find the sum of only number which is appended after the $ sign and the sum result should be from the input taken is 50040. The StringBiulder Object is coming in each loop but when I am trying to convert it to toString and trying to add it to the sum, getting the error.

required is convert the result to a number and add it to the sum that is not happening and I am getting the error:

java.lang.NumberFormatException: For input string: ""

My code:

package com.example.demo;

public class DemoApplication2 {
    public static void main(String args[]) {
        
        long sum=0;
        String str = new String("#1 Tickets $50,000 Received $40. Expenses. ChequE.");
        char chararray[] = str.toCharArray();

        for (int i = 0; i < chararray.length; i++) {
            StringBuilder someString = new StringBuilder();

            if (chararray[i] == '$') {
                for (int j = i+1; Character.isDigit(chararray[j]) || chararray[j] == ',' ; j++) {
                    if (Character.isDigit(chararray[j])) {
                        someString.append(chararray[j]);
                    }
                    i=j;
                }
                
            }
            System.out.println(someString.toString());
            sum=sum+Long.parseLong(someString.toString());
        }
    }
}

Getting the below Error:

    Exception in thread "main" java.lang.NumberFormatException: For input string: ""
        at java.base/java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
        at java.base/java.lang.Long.parseLong(Long.java:702)
        at java.base/java.lang.Long.parseLong(Long.java:817)
        at com.example.demo.DemoApplication2.main(DemoApplication2.java:27)

Answer 1

Here is the result of one of my tests.

The sum is 50040

One way to do this is to go through the String , checking for a dollar sign. When you find one, you set a boolean switch to true.

If the boolean switch is true, you get the next characters until you get to a stop character (period or space). I made the assumption based on your code that the number values would all be integer values and not floating-point values. Otherwise, you would use a Double conversion and a double sum.

I ignored the comma character and collected the digit characters into a StringBuilder . I converted the StringBuilder digits into a long value.

I put the stop characters into a separate method to document what they represent.

I put the StringBuilder to long conversion into a separate method because I execute that code twice. Once when I detect a stop character and once at the end of the String . I check at the end of the String in case a number value is at the end of the String with no stop character.

Here's the complete runnable code.

public class DemoApplication2 {

    public static void main(String[] args) {
        long sum = 0;
        String str = new String("#1 Tickets $50,000 Received $40. Expenses. ChequE.");
        char chararray[] = str.toCharArray();
        
        boolean isNumber = false;
        StringBuilder builder = new StringBuilder();

        for (int i = 0; i < chararray.length; i++) {
            if (isNumber) {
                if (chararray[i] == ',') {
                    continue;
                } else if (Character.isDigit(chararray[i])) {
                    builder.append(chararray[i]);
                } else if (isStopCharacter(chararray[i])) {
                    sum += valueOf(builder);
                    isNumber = false;
                }
            }
            
            if (chararray[i] == '$') {
                isNumber = true;
            }
        }
        
        sum += valueOf(builder);
        System.out.println("The sum is " + sum);
    }
    
    public static boolean isStopCharacter(char c) {
        return c == ' ' || c == '.';
    }
    
    public static long valueOf(StringBuilder builder) {
        long value = 0L;
        if (builder.length() > 0) {
            value = Long.valueOf(builder.toString());
            builder.delete(0, builder.length());
        }
        
        return value;
    }

}