蓝桥杯-十进制转十六进制

import java.util.ArrayList;
import java.util.Scanner;

public class Main {
    public static void main(String[] args){

        int i;
        Scanner sc = new Scanner(System.in);
        i = sc.nextInt();

        int[] a = new int[100];
        boolean t = true;
        int j =0;
        char ch[] = {'A', 'B', 'C', 'D', 'E', 'F'};
        ArrayList<Integer> result = new ArrayList<Integer>();
        if (i==0){
            result.add(0);
        }else
        while(t){
            if (i==0){
                break;
            }
                a[j] = i%16;
                result.add(a[j]);
                i = i/16;
                j++;
            }

        for (int n=result.size()-1;n>=0;n--){

            if (result.get(n)>=10){
                System.out.print(ch[a[n]-10]);
            }else{
                System.out.print(result.get(n));
            }
        }
    }
}

或者直接调用API（这TM是得对API有多熟？！）

import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        Integer n = in.nextInt();
        in.close();
        System.out.println(Integer.toHexString(n).toUpperCase());
    }
}