项目总结 生成19位 uuid工具类

import java.util.HashMap;
import java.util.Map;
import java.util.UUID;

public class Numbers {  
      
    final static char[] digits = { '0', '1', '2', '3', '4', '5', '6', '7', '8',  
            '9', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l',  
            'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y',  
            'z', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L',  
            'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y',  
            'Z' };  
  
    final static Map<Character, Integer> digitMap = new HashMap<Character, Integer>();  
  
    static {  
        for (int i = 0; i < digits.length; i++) {  
            digitMap.put(digits[i], (int) i);  
        }  
    }  
  
    /** 
     * 支持的最大进制数 
     */  
    public static final int MAX_RADIX = digits.length;  
  
    /** 
     * 支持的最小进制数 
     */  
    public static final int MIN_RADIX = 2;  
  
    /** 
     * 将长整型数值转换为指定的进制数（最大支持62进制，字母数字已经用尽） 
     *  
     * @param i 
     * @param radix 
     * @return 
     */  
    public static String toString(long i, int radix) {  
        if (radix < MIN_RADIX || radix > MAX_RADIX)  
            radix = 10;  
        if (radix == 10)  
            return Long.toString(i);  
  
        final int size = 65;  
        int charPos = 64;  
  
        char[] buf = new char[size];  
        boolean negative = (i < 0);  
  
        if (!negative) {  
            i = -i;  
        }  
  
        while (i <= -radix) {  
            buf[charPos--] = digits[(int) (-(i % radix))];  
            i = i / radix;  
        }  
        buf[charPos] = digits[(int) (-i)];  
  
        if (negative) {  
            buf[--charPos] = '-';  
        }  
  
        return new String(buf, charPos, (size - charPos));  
    }  
  
    static NumberFormatException forInputString(String s) {  
        return new NumberFormatException("For input string: \"" + s + "\"");  
    }  
  
    /** 
     * 将字符串转换为长整型数字 
     *  
     * @param s 
     *            数字字符串 
     * @param radix 
     *            进制数 
     * @return 
     */  
    public static long toNumber(String s, int radix) {  
        if (s == null) {  
            throw new NumberFormatException("null");  
        }  
  
        if (radix < MIN_RADIX) {  
            throw new NumberFormatException("radix " + radix  
                    + " less than Numbers.MIN_RADIX");  
        }  
        if (radix > MAX_RADIX) {  
            throw new NumberFormatException("radix " + radix  
                    + " greater than Numbers.MAX_RADIX");  
        }  
  
        long result = 0;  
        boolean negative = false;  
        int i = 0, len = s.length();  
        long limit = -Long.MAX_VALUE;  
        long multmin;  
        Integer digit;  
  
        if (len > 0) {  
            char firstChar = s.charAt(0);  
            if (firstChar < '0') {  
                if (firstChar == '-') {  
                    negative = true;  
                    limit = Long.MIN_VALUE;  
                } else if (firstChar != '+')  
                    throw forInputString(s);  
  
                if (len == 1) {  
                    throw forInputString(s);  
                }  
                i++;  
            }  
            multmin = limit / radix;  
            while (i < len) {  
                digit = digitMap.get(s.charAt(i++));  
                if (digit == null) {  
                    throw forInputString(s);  
                }  
                if (digit < 0) {  
                    throw forInputString(s);  
                }  
                if (result < multmin) {  
                    throw forInputString(s);  
                }  
                result *= radix;  
                if (result < limit + digit) {  
                    throw forInputString(s);  
                }  
                result -= digit;  
            }  
        } else {  
            throw forInputString(s);  
        }  
        return negative ? result : -result;  
    }  
    private static String digits(long val, int digits) {  
        long hi = 1L << (digits * 4);  
        return Numbers.toString(hi | (val & (hi - 1)), Numbers.MAX_RADIX)  
                .substring(1);  
    }  
    /** 
     * 以62进制（字母加数字）生成19位UUID，最短的UUID 
     *  
     * @return 
     */  
    public static String uuid() {  
        UUID uuid = UUID.randomUUID();  
        StringBuilder sb = new StringBuilder();  
        sb.append(digits(uuid.getMostSignificantBits() >> 32, 8));  
        sb.append(digits(uuid.getMostSignificantBits() >> 16, 4));  
        sb.append(digits(uuid.getMostSignificantBits(), 4));  
        sb.append(digits(uuid.getLeastSignificantBits() >> 48, 4));  
        sb.append(digits(uuid.getLeastSignificantBits(), 12));  
        return sb.toString();  
    }  
}