JAVA编程实现随机生成指定长度的密码功能【大小写和数字组合】

import java.util.Random;
public class PassWordCreate {
  /**
   * 获得密码
   * @param len 密码长度
   * @return
   */
  public String createPassWord(int len){
    int random = this.createRandomInt();
    return this.createPassWord(random, len);
  }
  public String createPassWord(int random,int len){
    Random rd = new Random(random);
    final int maxNum = 62;
    StringBuffer sb = new StringBuffer();
    int rdGet;//取得随机数
    char[] str = { 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k',
        'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w',
        'x', 'y', 'z', 'A','B','C','D','E','F','G','H','I','J','K',
        'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W',
        'X', 'Y' ,'Z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' };
    int count=0;
    while(count < len){
      rdGet = Math.abs(rd.nextInt(maxNum));//生成的数最大为62-1
      if (rdGet >= 0 && rdGet < str.length) {
        sb.append(str[rdGet]);
        count ++;
      }
    }
    return sb.toString();
  }
  public int createRandomInt(){
    //得到0.0到1.0之间的数字，并扩大100000倍
    double temp = Math.random()*100000;
    //如果数据等于100000，则减少1
    if(temp>=100000){
      temp = 99999;
    }
    int tempint = (int)Math.ceil(temp);
    return tempint;
  }
  public static void main(String[] args){
    PassWordCreate pwc = new PassWordCreate();
    System.out.println(pwc.createPassWord(8));
  }
}