java短链生成工具类

﹏ヽ暗。殇╰゛Y 2024-04-25 08:43 66阅读 0赞

## 一、代码 ##

public class Base62Utils {
    
        private static final String BASE_DIGITS = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
    
        private static final int BASE_DIGITS_SIZE = BASE_DIGITS.length();
    
        private static final char[] DIGITS_CHAR = BASE_DIGITS.toCharArray();
    
        private static final int FAST_SIZE = 'z';
    
        private static final int[] DIGITS_INDEX = new int[FAST_SIZE + 1];
    
        static {
            for (int i = 0; i < FAST_SIZE; i++) {
                DIGITS_INDEX[i] = -1;
            }
    
            for (int i = 0; i < BASE_DIGITS_SIZE; i++) {
                DIGITS_INDEX[DIGITS_CHAR[i]] = i;
            }
        }
    
        public static long decode(String s) {
            long result = 0L;
            long multiplier = 1;
            for (int pos = s.length() - 1; pos >= 0; pos--) {
                int index = getIndex(s, pos);
                result += index * multiplier;
                multiplier *= BASE_DIGITS_SIZE;
            }
            return result;
        }
    
        public static String encode(long number) {
            if (number < 0)
                throw new IllegalArgumentException("Number(Base62) must be positive: " + number);
            if (number == 0)
                return "0";
            StringBuilder buf = new StringBuilder();
            while (number != 0) {
                buf.append(DIGITS_CHAR[(int) (number % BASE_DIGITS_SIZE)]);
                number /= BASE_DIGITS_SIZE;
            }
            return buf.reverse().toString();
        }
    
        private static int getIndex(String s, int pos) {
            char c = s.charAt(pos);
            if (c > FAST_SIZE) {
                throw new IllegalArgumentException("Unknow character for Base62: " + s);
            }
            int index = DIGITS_INDEX[c];
            if (index == -1) {
                throw new IllegalArgumentException("Unknow character for Base62: " + s);
            }
            return index;
        }
    
    }

## 二、使用方法 ##

1.可以调用工具类的encode方法，输入一个长数字，返回一个短字符串  
2.可以调用工具类的decode方法，输入一个短字符串，输出一个长数字