java随机生成字符串

https://github.com/yhqmcq/infox-cms/blob/master/src/main/java/com/infox/common/util/RandomUtils.java

有修改

package com.pandy.net;

import java.util.Random;

/**
 * 项目名称: wp_idea_linux
 * 功能说明:
 * 创建者: Pandy,
 * 邮箱: [e-mail], [e-mail]
 * 版权:
 * 官网:
 * 创建日期: 15-10-13.
 * 创建时间: 上午11:35.
 * 修改历史:
 * -----------------------------------------------
 */
public class RandomUtils {

    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();
        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 generateNumber(int length) {
        StringBuffer sb = new StringBuffer();
        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
     *            随机字符串长度
     * @return 随机字符串
     */
    public static String generateMixString(int length) {
        StringBuffer sb = new StringBuffer();
        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
     *            随机字符串长度
     * @return 随机字符串
     */
    public static String generateLowerString(int length) {
        return generateString(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
     *            随机字符串长度
     * @return 随机字符串
     */
    public static String generateUpperString(int length) {
        return generateString(length).toUpperCase();
    }

    /**
     * 生成一个定长的纯0字符串
     *
     * @param length
     *            字符串长度
     * @return 纯0字符串
     */
    public 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();
    }

    /**
     * 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(int 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("generateNumber="+generateNumber(4));
        System.out.println("generateString="+generateString(15));
        System.out.println("generateMixString="+generateMixString(15));
        System.out.println("generateLowerString="+generateLowerString(15));
        System.out.println("generateUpperString="+generateUpperString(15));
        System.out.println("generateZeroString="+generateZeroString(15));
        System.out.println("toFixdLengthString="+toFixdLengthString(123, 15));
        System.out.println("toFixdLengthString="+toFixdLengthString(123L, 15));
    }

}