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package eleme.openapi.sdk.media.trace;

import java.util.UUID;

/**
 * Created by huamulou on 16/1/12.
 */
public class ShorterUUID {

    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 uuid
     */
    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();
    }
}