常用的获取随机字符串

package com.tianren.util;
import java.util.Random;  
 
/** 
 * RandomString.java 
 * utils class 
 * @author jinxx
 * @version 1.0  2009-6-10
 * */ 
public class RandomString {  
      
    /**返回大写随机字母字符串*/ 
    public static String getRandomStringU(int length){  
        String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";  
        Random random = new Random();  
        StringBuffer sb = new StringBuffer();  
        for(int i=0;i<length;++i){  
            int number = random.nextInt(26);  
            sb.append(str.charAt(number));  
        }         
        return sb.toString();  
    }  
      
    /**返回小写随机字母字符串*/ 
    public static String getRandomStringL(int length){  
        String str = "abcdefghijklmnopqrstuvwxyz";  
        Random random = new Random();  
        StringBuffer sb = new StringBuffer();  
        for(int i=0;i<length;++i){  
            int number = random.nextInt(26);  
            sb.append(str.charAt(number));  
        }         
        return sb.toString();  
    }  
      
    /**返回随机数字字符串[0-9]*/ 
    public static String getRandomStringN10(int length){  
        String str = "0123456789";  
        Random random = new Random();  
        StringBuffer sb = new StringBuffer();  
        for(int i=0;i<length;++i){  
            int number = random.nextInt(10);  
            sb.append(str.charAt(number));  
        }         
        return sb.toString();
    }  
      
    /**返回随机数字字符串[1-9]*/ 
    public static String getRandomStringN9(int length){  
        String str = "123456789";  
        Random random = new Random();  
        StringBuffer sb = new StringBuffer();  
        for(int i=0;i<length;++i){  
            int number = random.nextInt(9);  
            sb.append(str.charAt(number));  
        }         
        return sb.toString();  
    }  
      
    /**返回随机数字[1-9]*/ 
    public static int getRandomIntN9(int length){  
        String str = "123456789";  
        Random random = new Random();  
        StringBuffer sb = new StringBuffer();  
        for(int i=0;i<length;++i){  
            int number = random.nextInt(9);  
            sb.append(str.charAt(number));  
        }         
        return Integer.parseInt(sb.toString());  
    }  
      
    /**返回随机数字[0-9]*/ 
    public static int getRandomIntN10(int length){  
        String str = "0123456789";  
        Random random = new Random();  
        StringBuffer sb = new StringBuffer();  
        for(int i=0;i<length;++i){  
            int number = random.nextInt(10);  
            sb.append(str.charAt(number));  
        }         
        return Integer.parseInt(sb.toString());  
    }     
      
    /**返回大小写字母及数字混合的字符串*/ 
    public static String getRandomStringA(int length){  
        Random random = new Random();  
        StringBuffer sb = new StringBuffer();         
        for(int i = 0; i < length; ++i){  
            int number = random.nextInt(3);  
            long result = 0;  
            switch(number){  
            case 0:  
                result = Math.round(Math.random() * 25 + 64);  
                sb.append(String.valueOf((char)result));  
                break;  
            case 1:  
                result = Math.round(Math.random() * 25 + 97);  
                sb.append(String.valueOf((char)result));  
                break;  
            case 2:  
                sb.append(String.valueOf(new Random().nextInt(10)));  
                break;                
            }  
        }     
        return sb.toString();  
    }  
      
}