Java中高效处理数字字符串分组与求和：兼顾前导零显示

import java.util.ArrayList;

public class Grouping {
    public static int stringAdd(int length) {
        ArrayList<String> numbers = new ArrayList<>(); // 存储分组字符串
        String randomString = "";
        for (int i = 0; i < length; i++) {
            int randomNumbers = (int) (Math.random() * 10);
            randomString = randomString + randomNumbers;
        }
        System.out.println("Generated string: " + randomString);

        int group = 2;
        if (length > 30) {
            group = 3;
        }

        // 第一步：将分组存储到ArrayList
        for (int i = 0; i < length; i = i + group) {
            numbers.add(randomString.substring(i, Math.min(length, i + group)));
            System.out.println("Group (String): " + randomString.substring(i, Math.min(length, i + group)));
        }

        int[] array = new int[numbers.size()]; // 存储转换后的整数
        int total = 0;

        // 第二步：将ArrayList中的字符串转换为整数并求和
        for (int i = 0; i < numbers.size(); i++) {
            array[i] = Integer.parseInt(numbers.get(i));
            total = total + array[i];
        }
        return total;
    }

    public static void main(String[] args) {
        int randomLength = (int) (Math.random() * (50 - 25 + 1)) + 25;
        System.out.println("Length of the string is " + randomLength);
        System.out.println("Total: " + stringAdd(randomLength));
    }
}

Group: 5  (期望是 Group: 05)
Group: 3  (期望是 Group: 03)

public class Grouping {
    public static int stringAdd(int length) {
        String randomString = "";
        for (int i = 0; i < length; i++) {
            int randomNumbers = (int) (Math.random() * 10);
            randomString = randomString + randomNumbers;
        }
        System.out.println("Generated string: " + randomString);

        int group = 2;
        if (length > 30) {
            group = 3;
        }

        int total = 0; // 直接在这里累加总和
        for (int i = 0; i < length; i += group) { // 单个循环处理所有逻辑
            // 提取子字符串（分组）
            final String substring = randomString.substring(i, Math.min(length, i + group));

            // 关键：先打印字符串形式，保留前导零
            System.out.println("Group: " + substring); 

            // 再将字符串解析为整数，用于求和
            int digits = Integer.parseInt(substring);
            total += digits; // 累加到总和
        }
        return total;
    }

    public static void main(String[] args) {
        int randomLength = (int) (Math.random() * (50 - 25 + 1)) + 25; // 生成25到50之间的随机长度
        System.out.println("Length of the string is " + randomLength);
        System.out.println("Total: " + stringAdd(randomLength));
    }
}