如何在java項目中實現(xiàn)一個隨機數(shù)生產(chǎn)算法

package test;

import java.util.Random;

public class RandomUtil {

  public static final String ALLCHAR = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
  public static final String LETTERCHAR = "abcdefghijkllmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
  public static final String NUMBERCHAR = "0123456789";

  /** 
   * 返回一個定長的帶因子的固定的隨機字符串(只包含大小寫字母、數(shù)字)
   * 
   * @param length 
   *      隨機字符串長度 
   * @return 隨機字符串 
   */
  public static String generateStringByKey(int length, int channel) {
    StringBuffer sb = new StringBuffer();
    Random random = new Random(channel);
    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字符串(只包含大小寫字母、數(shù)字)
   * 
   * @param length 
   *      隨機字符串長度 
   * @return 隨機字符串 
   */
  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 
   */
  public static 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 
   */
  public static 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 
   */
  public static 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 
   */
  public static String generateZeroString(int length) {
    StringBuffer sb = new StringBuffer();
    for (int i = 0; i < length; i++) {
      sb.append('0');
    }
    return sb.toString();
  }

  /** 
   * 根據(jù)數(shù)字生成一個定長的字符串，長度不夠前面補0 
   * 
   * @param num 
   *      數(shù)字 
   * @param fixdlenth 
   *      字符串長度 
   * @return 定長的字符串 
   */
  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("將數(shù)字" + num + "轉(zhuǎn)化為長度為" + fixdlenth + "的字符串發(fā)生異常！");
    }
    sb.append(strNum);
    return sb.toString();
  }

  /** 
   * 每次生成的len位數(shù)都不相同 
   * 
   * @param param 
   * @return 定長的數(shù)字 
   */
  public static int 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;
  }

  public static void main(String[] args) {
    int channel = 555555;// 測試因子比生產(chǎn)因子少1
    System.out.println("返回一個定長的帶因子的固定的隨機字符串(只包含大小寫字母、數(shù)字):" + generateStringByKey(32, channel));
    System.out.println("返回一個定長的隨機字符串(只包含大小寫字母、數(shù)字):" + generateString(32));
    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(jù)數(shù)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(shù)都不相同:" + getNotSimple(in, 3));
  }
}