Java方法solve执行报错java.lang.IndexOutOfBoundsException求排查

Hey there! Let's break down why your code is throwing that java.lang.IndexOutOfBoundsException and fix it to meet your goal of finding the largest number in a mixed letter-digit string.

First, the root cause of the IndexOutOfBoundsException #

Your second loop has two critical issues:

• Wrong loop condition: You're using strArr.length (a fixed value) as the loop limit, but arr gets smaller every time you call remove(). Once i exceeds the current size of arr, calling arr.remove(i) will trigger the index out-of-bounds error.
• Broken check logic: Character.isLetter(i) is checking if the loop index (an integer like 0,1,2...) is a letter—this makes no sense! You meant to check characters in the string, not the loop counter.

Beyond the exception: Your core logic is misaligned with the goal #

Using s.split("\"") to split the string by double quotes has nothing to do with extracting digits from a mixed string. If your input has no quotes, this just gives you the original string as a single element, which doesn't help you separate numbers from letters at all.

Fixed code that works as intended #

Let's rewrite the logic to properly extract all continuous digit sequences, convert them to integers, and find the maximum:

import java.util.ArrayList;
import java.util.Collections;

public class DigitExtractor {

    public ArrayList<Integer> getIntArray(ArrayList<String> stringArray) {
        ArrayList<Integer> result = new ArrayList<>();
        for (String stringVal : stringArray) {
            // Guard against non-digit strings to avoid NumberFormatException
            if (stringVal.matches("\\d+")) {
                result.add(Integer.parseInt(stringVal));
            }
        }
        return result;
    }

    public int solve(String s) {
        ArrayList<String> numStrings = new ArrayList<>();
        StringBuilder currentNumber = new StringBuilder();

        // Traverse each character to collect continuous digit sequences
        for (char c : s.toCharArray()) {
            if (Character.isDigit(c)) {
                currentNumber.append(c);
            } else {
                // If we were collecting digits, add the sequence to our list and reset
                if (currentNumber.length() > 0) {
                    numStrings.add(currentNumber.toString());
                    currentNumber.setLength(0);
                }
            }
        }
        // Don't forget to add the last digit sequence if the string ends with digits
        if (currentNumber.length() > 0) {
            numStrings.add(currentNumber.toString());
        }

        ArrayList<Integer> intArr = getIntArray(numStrings);
        // Handle edge case where input has no digits
        if (intArr.isEmpty()) {
            throw new IllegalArgumentException("Input string contains no numeric values");
        }
        return Collections.max(intArr);
    }

    // Test the code
    public static void main(String[] args) {
        DigitExtractor extractor = new DigitExtractor();
        System.out.println(extractor.solve("abc123def45xyz789")); // Outputs 789
        System.out.println(extractor.solve("hello1world22test333")); // Outputs 333
    }
}

Key fixes explained #

• Proper digit extraction: We iterate through each character in the input string, building up sequences of digits. When we hit a non-digit, we save the current digit sequence (if any) and reset our builder.
• Safe collection handling: We avoid modifying a list while iterating over a fixed length—instead, we build the list of digit strings first, then convert them.
• Error protection: We add checks to avoid converting non-digit strings (preventing NumberFormatException) and handle the case where the input has no digits at all.

内容的提问来源于stack exchange，提问作者Ayaan Siddiqui