生成id

package test;

import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.util.UUID;

public class IdUtil {
    private final static int HASH_LENGTH = 7;
    private static String[] chars = new String[] {
        "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",
        "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" };

    /**
     * 得到一个8位的随机串
     * @return
     */
    private static String getShortUuid() {
        StringBuffer buffer = new StringBuffer();
        String uuid = UUID.randomUUID().toString().replace("-", "");
        for (int i = 0; i < 8; i++) {
            String str = uuid.substring(i * 4, i * 4 + 4);
            int x = Integer.parseInt(str, 16);
            buffer.append(chars[x % 0x3E]);
        }
        return buffer.toString();
    }

    /**
     * 得到一个7位的threadhash
     * @return
     */
    private static String getThreadHash(){
        String hash = String.valueOf(Thread.currentThread().hashCode());
        if(hash.length() != HASH_LENGTH){
            hash = dealHash(hash);
        }
        return hash;
    }

    /**
     * 处理hash长度
     * @param hash
     * @return
     */
    private static String dealHash(String hash){
        //如果长度大于HASH_LENGTH，取HASH_LENGTH位长度
        if(hash.length() > HASH_LENGTH){
            hash = hash.substring(hash.length() - HASH_LENGTH, hash.length());
        }else{
            //如果长度小于HASH_LENGTH，前边补0
            int diff = HASH_LENGTH - hash.length();
            StringBuffer buffer = new StringBuffer();
            for(int i=0;i<diff;i++){
                buffer.append(0);
            }
            buffer.append(hash);
            hash = buffer.toString();
        }
        return hash;
    }

    /**
     * 得到一个32位的id[jdk1.8的时间类型，如果低版本jdk，需要重写时间相关]
     * 时间+线程hash+随机串
     * @return
     */
    public static String getId(){
        LocalDateTime localDateTime = LocalDateTime.now();
        DateTimeFormatter formartter = DateTimeFormatter.ofPattern("yyyyMMddHHmmssSSS");
        String current = formartter.format(localDateTime);

        StringBuffer buffer = new StringBuffer(32);
        buffer.append(current);
        buffer.append(getThreadHash());
        buffer.append(getShortUuid());

        System.out.println("ID:" + buffer.toString());

        return buffer.toString();
    }

    public static void main(String[] args) {
        getId();
    }
}