Скачать или смотреть How to Find the Sum from a String of Numbers in Java

A simple guide on how to correctly sum digits extracted from a string in Java, along with explanations of ASCII values and numeric conversion.
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Understanding the Problem: Summing Digits in a String

If you've ever tried summing numbers embedded in a string in Java, you may have encountered issues with unexpected results. For instance, in a recent scenario where a programmer tried to sum the digits from the string "12345", they ended up with a total of 255 instead of the intended sum of 15. This discrepancy arises from how characters are treated in Java. When summing character values directly, the result can be misleading due to ASCII values.

In this guide, we will break down the correct way to sum digits found in a string and clarify concepts that will help you avoid common mistakes.

The Step-by-Step Solution

To resolve the problem of summing the digits from a string, we can follow a systematic approach. Here's how you can effectively execute this task:

1. Initialize the Sum Variable

Before starting the summation process, you should set up a sum variable to accumulate your results:

[[See Video to Reveal this Text or Code Snippet]]

2. Loop Through Each Character of the String

Next, you'll want to iterate over each character in the string. This involves using a loop to check every single character. Here's a simple way to do this:

[[See Video to Reveal this Text or Code Snippet]]

3. Check If the Character is a Digit

To ensure that you're only summing numeric characters, you can leverage Java's built-in method Character.isDigit(char c). This method checks if the character you are looking at is a digit (0-9):

[[See Video to Reveal this Text or Code Snippet]]

4. Convert the Character to a Numeric Value

Characters representing digits need to be converted to their numeric values. To do this, you can subtract the character '0' from the digit character. This provides an easy conversion from ASCII values to actual integers:

[[See Video to Reveal this Text or Code Snippet]]

Complete Code Example

Here’s how all of these steps look together in a complete Java program:

[[See Video to Reveal this Text or Code Snippet]]

Understanding the Subtraction of '0'

It's essential to grasp why we subtract '0' from the character. In the ASCII table, the digit characters ('0' to '9') have specific numeric values starting from 48. Here's a quick reference:

'0' - ASCII 48

'1' - ASCII 49

'2' - ASCII 50

...

'9' - ASCII 57

When you subtract '0' (48) from any digit, you effectively convert that character to its numeric value. For example, if c is '1', the calculation c - '0' gives you 49 - 48 = 1.

Conclusion

By following this structured method for summing digits in a string, you can avoid issues with unexpected results. Key takeaways include understanding the importance of checking if a character is a digit and converting characters correctly to their numerical forms. For larger numbers, you can also utilize the Integer.parseInt() method for direct conversion of whole number strings into integers.

Hopefully, this guide helps you successfully find sums of digits in strings while avoiding common pitfalls along the way. Happy coding!