蓝桥杯- 基础练习：十六进制转八进制

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int size = scanner.nextInt();
        String[] strings = new String[size];
        for (int i = 0; i < strings.length; i++) {
            strings[i] = scanner.next();
        }

        for (int i = 0; i < strings.length; i++) {
            toBinaryString(strings[i]);
        }
    }

    private static void toBinaryString(String string) {
        String str = string.toUpperCase();
        char[] chars = str.toCharArray();
        StringBuffer buffer = new StringBuffer();
        for (int i = 0; i < chars.length; i++) {
            
            switch (chars[i]) {
                    case '0':
                        buffer.append("0000");
                        break;
                    case '1':
                        buffer.append("0001");
                        break;
                    case '2':
                        buffer.append("0010");
                        break;
                    case '3':
                        buffer.append("0011");
                        break;
                    case '4':
                        buffer.append("0100");
                        break;
                    case '5':
                        buffer.append("0101");
                        break;
                    case '6':
                        buffer.append("0110");
                        break;
                    case '7':
                        buffer.append("0111");
                        break;
                    case '8':
                        buffer.append("1000");
                        break;
                    case '9':
                        buffer.append("1001");
                        break;
                    case 'A':
                        buffer.append("1010");
                        break;
                    case 'B':
                        buffer.append("1011");
                        break;
                    case 'C':
                        buffer.append("1100");
                        break;
                    case 'D':
                        buffer.append("1101");
                        break;
                    case 'E':
                        buffer.append("1110");
                        break;
                    case 'F':
                        buffer.append("1111");
                        break;
            }
        }
        
        toOctalString(buffer);
    }

    private static void toOctalString(StringBuffer buffer) {
        int len = buffer.length();
        if(len%3==0) {
            if(buffer.substring(0,3).equals("000")) {
                buffer.delete(0, 3);
            }
        }
        
        if(len%3==1) {
            if(buffer.substring(0,1).equals("0")) {
                buffer.delete(0, 1);
            }else {
                buffer.insert(0, "00");
            }
        }
        
        if(len%3==2) {
            if(buffer.substring(0,2).equals("00")) {
                buffer.delete(0, 2);
            }else {
                buffer.insert(0, "0");
            }
        }
        
        StringBuffer stringBuffer = new StringBuffer();
        
        for (int i = 0; i < buffer.length()/3; i++) {
            
            String substring = buffer.substring(i*3,i*3+3);
        
            switch (substring) {
            
            case "000":
                stringBuffer.append("0");
                break;
            case "001":
                stringBuffer.append("1");
                break;
            case "010":
                stringBuffer.append("2");
                break;
            case "011":
                stringBuffer.append("3");
                break;
            case "100":
                stringBuffer.append("4");
                break;
            case "101":
                stringBuffer.append("5");
                break;
            case "110":
                stringBuffer.append("6");
                break;
            case "111":
                stringBuffer.append("7");
                break;
            }
        }
        System.out.println(stringBuffer.toString());
    }
}