java获取指定长度随机数

package org.sw;

import java.util.Random;

/**
 * 得到指定位数的随机数
 * @author mengzw
 * @since 3.0 2014-2-28
 */
public class DemoRandom {

    /**
     * 获取随机数
     * @param length
     * @return
     */
    public String getCharAndNumr(int length)     
    {     
        String val = "";     
                 
        Random random = new Random();     
        for(int i = 0; i < length; i++)     
        {     
            String charOrNum = random.nextInt(2) % 2 == 0 ? "char" : "num"; // 输出字母还是数字     
                     
            if("char".equalsIgnoreCase(charOrNum)) // 字符串     
            {     
                int choice = random.nextInt(2) % 2 == 0 ? 65 : 97; //取得大写字母还是小写字母     
                val += (char) (choice + random.nextInt(26));     
            }     
            else if("num".equalsIgnoreCase(charOrNum)) // 数字     
            {     
                val += String.valueOf(random.nextInt(10));     
            }     
        }     
                 
        return val;     
    }   
    
    public static void main(String[] args) {
        DemoRandom dr = new DemoRandom();
        String random = dr.getCharAndNumr(13);
        System.out.println(random);
    }
}