如何将BigInteger转换为固定长度的十六进制？

import java.math.BigInteger;

public class BigIntegerToFixedHex {
    public static void main(String[] args) {
        BigInteger bigInteger = new BigInteger("1234567890");

        // 将BigInteger转换为十六进制字符串
        String hexString = bigInteger.toString(16);

        // 将十六进制字符串转换为固定长度的十六进制
        String fixedHex = padLeft(hexString, 32, '0');

        System.out.println("BigInteger: " + bigInteger);
        System.out.println("Fixed Hex: " + fixedHex);
    }

    // 在字符串左侧填充指定字符，直到达到指定长度
    private static String padLeft(String input, int length, char paddingChar) {
        StringBuilder sb = new StringBuilder(input);
        while (sb.length() < length) {
            sb.insert(0, paddingChar);
        }
        return sb.toString();
    }
}