Java随机数生成工具类［转载］

package cn.module;
public class Random {
    public static final String allChar = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
    public static final String letterChar = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
    public static final String numberChar = "0123456789";
    
    /**
     * 返回一个定长的随机字符串(只包含大小写字母、数字)
     * @param    length    随机字符串长度
     * @return 随机字符串
     * */
    public static String generateString(int length) {
        StringBuffer sb = new StringBuffer();
        java.util.Random r = new java.util.Random();
        for (int i = 0; i < length; i++) {
            sb.append(allChar.charAt(r.nextInt(allChar.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 随机字符串长度
     * @return 随机字符串
     */
    public static String generateMixString(int length) {
        StringBuffer sb = new StringBuffer();
        java.util.Random r = new java.util.Random();
        for (int i = 0; i < length; i++) {
            sb.append(letterChar.charAt(r.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 随机字符串长度
     * @return 随机字符串
     */
    public static String generateLowerString(int length) {
        return generateMixString(length).toLowerCase();
    }
    
    private static String generateZeroString(int length) {
        StringBuffer sb = new StringBuffer();
        for (int i = 0; i < length; i++) {
                sb.append('0');
        }
        return sb.toString();
    }
    
    /**
     * 根据数字生成一个定长的字符串，长度不够前面补0
     *
     * @param num 数字
     * @param fixdlenth 字符串长度
     * @return 定长的字符串
     */
    public static String toFixdLengthString(long num, int fixdlenth) {
        StringBuffer sb = new StringBuffer();
        String strNum = String.valueOf(num);
        if (fixdlenth - strNum.length() >= 0) {
                sb.append(generateZeroString(fixdlenth - strNum.length()));
        } else {
                throw new RuntimeException("将数字" + num + "转化为长度为" + fixdlenth + "的字符串发生异常！");
        }
        sb.append(strNum);
        return sb.toString();
}
    public static void main(String[] args) {
        System.out.println(generateString(5));
    }
}



以后可以直接调用此工具类操作！