隨機數產生

代碼如下：

package com.zuidaima.core.util;

import java.util.Random;

publicclass RandomUtil {
publicstaticfinal String ALLCHAR = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
publicstaticfinal String LETTERCHAR = "abcdefghijkllmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
publicstaticfinal String NUMBERCHAR = "0123456789";

/**
     * 返回一個定長的隨機字符串(只包含大小寫字母、數字)
     *
     * @param length
     *            隨機字符串長度
     * @return 隨機字符串
     */
publicstatic 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();
    }

/**
     * 返回一個定長的隨機純字母字符串(只包含大小寫字母)
     *
     * @param length
     *            隨機字符串長度
     * @return 隨機字符串
     */
publicstatic String generateMixString(int length) {
        StringBuffer sb = new StringBuffer();
        Random random = new Random();
for (int i = 0; i < length; i++) {
            sb.append(ALLCHAR.charAt(random.nextInt(LETTERCHAR.length())));
        }
return sb.toString();
    }

/**
     * 返回一個定長的隨機純大寫字母字符串(只包含大小寫字母)
     *
     * @param length
     *            隨機字符串長度
     * @return 隨機字符串
     */
publicstatic String generateLowerString(int length) {
return generateMixString(length).toLowerCase();
    }

/**
     * 返回一個定長的隨機純小寫字母字符串(只包含大小寫字母)
     *
     * @param length
     *            隨機字符串長度
     * @return 隨機字符串
     */
publicstatic String generateUpperString(int length) {
return generateMixString(length).toUpperCase();
    }

/**
     * 生成一個定長的純0字符串
     *
     * @param length
     *            字符串長度
     * @return 純0字符串
     */
publicstatic String generateZeroString(int length) {
        StringBuffer sb = new StringBuffer();
for (int i = 0; i < length; i++) {
            sb.append('0');
        }
return sb.toString();
    }

/**
     * 根據數字生成一個定長的字符串，長度不夠前面補0
     *
     * @param num
     *            數字
     * @param fixdlenth
     *            字符串長度
     * @return 定長的字符串
     */
publicstatic 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 {
thrownew RuntimeException("將數字" + num + "轉化爲長度爲" + fixdlenth
                    + "的字符串發生異常！");
        }
        sb.append(strNum);
return sb.toString();
    }

/**
     * 每次生成的len位數都不相同
     *
     * @param param
     * @return 定長的數字
     */
publicstaticint getNotSimple(int[] param, int len) {
        Random rand = new Random();
for (int i = param.length; i > 1; i--) {
int index = rand.nextInt(i);
int tmp = param[index];
            param[index] = param[i - 1];
            param[i - 1] = tmp;
        }
int result = 0;
for (int i = 0; i < len; i++) {
            result = result * 10 + param[i];
        }
return result;
    }

publicstaticvoid main(String[] args) {
        System.out.println("返回一個定長的隨機字符串(只包含大小寫字母、數字):" + generateString(10));
        System.out
                .println("返回一個定長的隨機純字母字符串(只包含大小寫字母):" + generateMixString(10));
        System.out.println("返回一個定長的隨機純大寫字母字符串(只包含大小寫字母):"
                + generateLowerString(10));
        System.out.println("返回一個定長的隨機純小寫字母字符串(只包含大小寫字母):"
                + generateUpperString(10));
        System.out.println("生成一個定長的純0字符串:" + generateZeroString(10));
        System.out.println("根據數字生成一個定長的字符串，長度不夠前面補0:"
                + toFixdLengthString(123, 10));
int[] in = { 1, 2, 3, 4, 5, 6, 7 };
        System.out.println("每次生成的len位數都不相同:" + getNotSimple(in, 3));
    }
}

有圖有真相：