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package cn.ipokerface.weixin.utils;

import java.util.Random;
import java.util.UUID;

/**
 * Created by       PokerFace
 * Create Date      2019-12-28.
 * Email:           [email protected]
 * Version          1.0.0
 * 
 * Description:
 */
public class RandomUtil {

    private static final String ALLCHAR = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
    private static final String LETTERCHAR = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
    private static final String NUMBERCHAR = "0123456789";

    /**
     * 返回一个定长的随机字符串(包含数字和大小写字母)
     *
     * @param length
     *            随机数的长度
     * @return
     */
    public static String generateString(int length) {
        StringBuilder sb = new StringBuilder(length);
        Random random = new Random();
        for (int i = 0; i < length; i++) {
            sb.append(ALLCHAR.charAt(random.nextInt(ALLCHAR.length())));
        }
        return sb.toString();
    }

    /**
     * 返回一个定长的随机纯数字字符串(只包含数字)
     *
     * @param length
     *            随机数的长度
     * @return
     */
    public static String generateStringByNumberChar(int length) {
        StringBuilder sb = new StringBuilder(length);
        Random random = new Random();
        for (int i = 0; i < length; i++) {
            sb.append(NUMBERCHAR.charAt(random.nextInt(NUMBERCHAR.length())));
        }
        return sb.toString();
    }

    /**
     * 返回一个定长的随机纯字母字符串(只包含大小写字母)
     *
     * @param length
     *            随机数的长度
     * @return
     */
    public static String generateStringByLetterCharr(int length) {
        StringBuilder sb = new StringBuilder(length);
        Random random = new Random();
        for (int i = 0; i < length; i++) {
            sb.append(LETTERCHAR.charAt(random.nextInt(LETTERCHAR.length())));
        }
        return sb.toString();
    }

    /**
     * 返回一个定长的随机纯大写字母字符串(只包含大小写字母)
     *
     * @param length
     *            随机数的长度
     * @return
     */
    public static String generateLowerString(int length) {
        return generateStringByLetterCharr(length).toLowerCase();
    }

    /**
     * 返回一个定长的随机纯小写字母字符串(只包含大小写字母)
     *
     * @param length
     *            随机数的长度
     * @return
     */
    public static String generateUpperString(int length) {
        return generateStringByLetterCharr(length).toUpperCase();
    }

    /**
     * 随机获取UUID字符串(无中划线)
     *
     * @return UUID字符串
     */
    public static String getUUID() {
        String uuid = UUID.randomUUID().toString();
        return uuid.substring(0, 8) + uuid.substring(9, 13)
                + uuid.substring(14, 18) + uuid.substring(19, 23)
                + uuid.substring(24);
    }

    public static void main(String[] args) {
        System.out.println(System.nanoTime());
        System.out.println(System.currentTimeMillis());
    }
}