1 import java.util.Scanner;
2 public class Main{
3 public static void main(String[] args){
4 Scanner input = new Scanner(System.in);
5 int n;
6 n=input.nextInt();
7 System.out.println(Integer.toHexString(n).toUpperCase());//转换成大写字母；toLowerCase()：转换成小写的16进制；
8   }
9 }

 1 import java.util.Scanner;
 2 public class Main {
 3     public static void main(String[] args) {
 4         Scanner sc=new Scanner(System.in);
 5        String c=sc.next();
 6        System.out.println(Integer.toHexString(c).toUpperCase());//十进制转换成十六进制
 7         System.out.println(Integer.toBinaryString(c).toUpperCase());//十进制转换成2进制
 8         System.out.println(Integer.toOctalString(c).toUpperCase());//十进制转换成八进制
 9        System.out.println(Integer.valueOf(c,16).toString());//十六进制转换成十进制
10        String t=Integer.valueOf(c, 16).toString();
11        int n=Integer.parseInt(t);//先将十六进制转换成字符串然后将字符串转换成整数
12        System.out.println(Integer.toOctalString(n).toUpperCase());//整数转换成八进制
13     }
14 }

 1 #include <stdio.h>
 2 #include<cstring>
 3 int x2i(char c)
 4 {
 5     if (c >= ‘A‘)
 6         return c - 55;
 7     else
 8         return c - 48;
 9 }
10 
11 int main()
12 {
13     int i, j, n;
14     char a[10][100001];
15     scanf("%d", &n);
16     for (i = 0; i < n; i++)
17         scanf("%s", a[i]);
18     for (i = 0; i < n; i++)
19     {
20         char* p = a[i];
21         int len = strlen(p);
22         if (len % 3 == 1)
23         {
24             printf("%o", x2i(p[0]));
25             j = 1;
26         }
27         else if (len % 3 == 2)
28         {
29             printf("%o", x2i(p[0])*16+x2i(p[1]));
30             j = 2;
31         }
32         else
33         {
34             printf("%o", x2i(p[0])*256+x2i(p[1])*16+x2i(p[2]));
35             j = 3;
36         }
37         for (; j < len; j += 3)
38             printf("%04o", x2i(p[j])*256+x2i(p[j+1])*16+x2i(p[j+2]));
39         printf("\n");
40     }
41     return 0;
42 }