import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        String[] st = new String[n];
        for (int i = 0; i < n; i++) {
            st[i] = sc.next();
        }
        sc.close();
        for (int i = 0; i < n; i++) {
            String str1 = ttos(st[i]);
            int len_str1 = str1.length();
            if (len_str1 % 3 == 1) str1 = "00" + str1;
            else if (len_str1 % 3 == 2) str1 = "0" + str1;
            ttoe(str1);
            System.out.println();
        }
    }

    public static String ttos(String str) {
        int len_str = str.length();
        StringBuilder str2 = new StringBuilder();
        for (int i = 0; i < len_str; ++i) {
            switch (str.charAt(i)) {
                case ‘0‘:
                    str2.append("0000");
                    break;
                case ‘1‘:
                    str2.append("0001");
                    break;
                case ‘2‘:
                    str2.append("0010");
                    break;
                case ‘3‘:
                    str2.append("0011");
                    break;
                case ‘4‘:
                    str2.append("0100");
                    break;
                case ‘5‘:
                    str2.append("0101");
                    break;
                case ‘6‘:
                    str2.append("0110");
                    break;
                case ‘7‘:
                    str2.append("0111");
                    break;
                case ‘8‘:
                    str2.append("1000");
                    break;
                case ‘9‘:
                    str2.append("1001");
                    break;
                case ‘A‘:
                    str2.append("1010");
                    break;
                case ‘B‘:
                    str2.append("1011");
                    break;
                case ‘C‘:
                    str2.append("1100");
                    break;
                case ‘D‘:
                    str2.append("1101");
                    break;
                case ‘E‘:
                    str2.append("1110");
                    break;
                case ‘F‘:
                    str2.append("1111");
                    break;
                default:
                    break;
            }
        }
        return str2.toString();
    }

    public static void ttoe(String str2) {
        int len = str2.length();
        int a;
        a = (str2.charAt(0) - ‘0‘) * 4 + (str2.charAt(1) - ‘0‘) * 2 + (str2.charAt(2) - ‘0‘);
        if (a != 0) System.out.print(a);
        for (int i = 3; i <= len - 3; i += 3) {
            a = (str2.charAt(i) - ‘0‘) * 4 + (str2.charAt(i + 1) - ‘0‘) * 2 + (str2.charAt(i + 2) - ‘0‘);
            System.out.print(a);
        }
   
 
 }
}

在我解決藍橋練習的十六進制轉八進制的練習中，我想要使用Integer的parseInt方法來實現將16進制的數封裝到Integer對象中再輸出為8進制。

        Scanner sc = new Scanner(System.in);
        int n = Integer.valueOf(sc.nextLine());
        long[] a = new long[n];
        for (int i = 0; i < n; i++) {
            String s=sc.nextLine();
            a[i] = Integer.parseInt(s, 16);
        }
        for (long b : a) {
            System.out.println(Long.toOctalString(b));
        }
        sc.close();
 

運行小例子沒問題，但是送到系統出了錯。是parseInt()方法要封裝的數值超出了int的範圍。

例如：

　　parseInt(“2147483648”, 10) 拋出 NumberFormatException
　　parseInt(“99”, 8) 拋出 NumberFormatException
　　parseInt(“Kona”, 10) 拋出 NumberFormatException

藍橋杯 基礎練習 十六進制轉八進制