进制转换及回文判断

1、进制转换

十进制转二进制、八进制、十六进制
思想：辗转相除法

// 十进制转十六进制
    private static void decToHex(int num) {

        String hex = "";

        int shang = num;
        int yu;

        while(shang != 0) {
            yu = shang % 16;
            shang = shang / 16;

            char result;

            if(yu > 9)
                result = (char) ('A' + (yu - 10));
            else
                result = (char) ('0' + (yu - 0));

            hex = result + hex;
        }
        System.out.println(num + "的16进制: " + hex);
    }

    // 十进制转二进制
    private static void decToBinary(int num) {
        String binary = "";
        int yu;
        int shang = num;

        while(shang != 0) {
            yu = shang % 2;
            shang = shang / 2;

            binary = yu + binary;
        }
        System.out.println(num + " 的二进制: " + binary);
    }

    // 十进制转八进制
    private static void decToOct(int num) {
        String oct = "";
        int yu;
        int shang = num;

        while(shang != 0) {
            yu = shang % 8;
            shang = shang / 8;

            oct = yu + oct;
        }
        System.out.println(num + " 的八进制: " + oct);
    }

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2、回文判断

注意点：
  1、字符串长度可分为 奇数 和 偶数 两种
  2、边界值分析

	// 使用普通方式
    private static void isPlalindrome() {
        Scanner cin = new Scanner(System.in);
        System.out.println("输入目标字符串: ");
        String str = cin.nextLine();

        boolean isPalindrome = false;
        int begin = 0;
        int end = str.length() - 1;

        while (begin < end && str.charAt(begin) == str.charAt(end)) {
            begin ++;
            end --;
        }
        if (begin >= end)   // 奇偶数长度的字符串统一处理
            isPalindrome = true;

        System.out.println(str + (isPalindrome ? "" : "不") + "是一个回文字符串.");
    }