蓝桥基础十六进制转换成八进制题目（java），不明白错误在哪

import java.util.Scanner;

public class Main {
public String strBinary(String s) {
StringBuffer sBuffer = new StringBuffer();
for(int i = 0;i<s.length();i++) {
switch(s.charAt(i))
{
case '1' : sBuffer.append("0001");break;
case '2' : sBuffer.append("0010");break;
case '3' : sBuffer.append("0011");break;
case '4': sBuffer.append("0100");break;
case '5': sBuffer.append("0101");break;
case '6': sBuffer.append("0110");break;
case '7': sBuffer.append("0111");break;
case '8': sBuffer.append("1000");break;
case '9': sBuffer.append("1001");break;
case 'A': sBuffer.append("1010");break;
case 'B': sBuffer.append("1011");break;
case 'C': sBuffer.append("1100");break;
case 'D': sBuffer.append("1101");break;
case 'E': sBuffer.append("1110");break;
case 'F': sBuffer.append("1111");break;
default: break;
}
}
return sBuffer.toString();
}

public String strOcatal(String s) {
int k = 0;
StringBuffer stb = new StringBuffer();
if (s.substring(0, 3).equals("000")) k = 3;else k = 0;
for(int i = k;i<s.length()-2;i+=3) {
switch (Integer.valueOf(s.substring(i,i+3)))
{
case 000 : stb.append("0");break;
case 001 : stb.append("1");break;
case 010 : stb.append("2");break;
case 011 : stb.append("3");break;
case 100 : stb.append("4");break;
case 101 : stb.append("5");break;
case 110 : stb.append("6");break;
case 111 : stb.append("7");break;
}

}
return stb.toString();
}

public static void main(String[] args) {
    Scanner in = new Scanner(System.in);
    int n = in.nextInt();
    Main xMain = new Main();
    String str[] = new String[n+1];
    for(int i = 0;i<n;i++) {
        str[i] = in.next();
    }
    in.close();
    for(int i = 0;i<n;i++) {
        String x =xMain.strBinary(str[i]);
        if ((x.length()%3)==1) x = "00"+x;
        if ((x.length()%3)==2) x = "0"+x;
        String y = xMain.strOcatal(x);
        System.out.println(y);
    }

}}

代码如上
蓝桥的输入数据很变态超长，但是题目中给出的数据都能成功，不明白错误在哪，诚心请求大佬指教

 import java.util.*;
public class Main{
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        String[] sts = new String[n];
        for(int i=0;i<n;i++){
            sts[i] = sc.next();
        }
        sc.close();
        for(int i=0;i<n;i++){
            String strBinary = toBinary(sts[i]);
            int len_strBin = strBinary.length();
            if(len_strBin%3==1) strBinary = "00"+strBinary;
            if(len_strBin%3==2) strBinary = "0"+strBinary;
            String strOctal = toOctal(strBinary);
            System.out.println(strOctal);
        }
    }
    private static String toOctal(String strBinary) {
        int len = strBinary.length();
        int k;
        StringBuffer stb = new StringBuffer();
        if(strBinary.substring(0, 3).equals("000"))
            k=3;
        else
            k=0;
        for(int i=k;i<len-2;i+=3){
            switch (strBinary.substring(i, i+3)) {
                case "000":stb.append("0");break;
                case "001":stb.append("1");break;
                case "010":stb.append("2");break;
                case "011":stb.append("3");break;
                case "100":stb.append("4");break;
                case "101":stb.append("5");break;
                case "110":stb.append("6");break;
                case "111":stb.append("7");break;
                default:break;
            }
        }
        return stb.toString();
    }
    private static String toBinary(String strHex) {
        int len_str = strHex.length();
        StringBuffer stb = new StringBuffer();
        for(int i=0;i<len_str;i++){
            switch (strHex.charAt(i)) {
                case '0':stb.append("0000");break;
                case '1':stb.append("0001");break;
                case '2':stb.append("0010");break;
                case '3':stb.append("0011");break;
                case '4':stb.append("0100");break;
                case '5':stb.append("0101");break;
                case '6':stb.append("0110");break;
                case '7':stb.append("0111");break;
                case '8':stb.append("1000");break;
                case '9':stb.append("1001");break;
                case 'A':stb.append("1010");break;
                case 'B':stb.append("1011");break;
                case 'C':stb.append("1100");break;
                case 'D':stb.append("1101");break;
                case 'E':stb.append("1110");break;
                case 'F':stb.append("1111");break;
                default:break;
            }
        }
        return stb.toString();
    }
}