【java】性能翻倍的超短19位UUID生成工具类

来源：互联网发布：kmp算法严蔚敏编辑：程序博客网时间：2024/06/06 16:44
package p2p.utils;import java.util.HashMap;import java.util.Map;import java.util.UUID;public class UuidUtil {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;}/** * 编写uuid生成工具方法 * @param val * @param digits * @return */public static String digits(long val, int digits) {long hi = 1L << (digits * 4);return toString(hi | (val & (hi - 1)), 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();}}
0 0