Java+Selenium——如何点击菜单下子菜单

package rjcs;

import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.List;
import java.util.Set;

import org.openqa.selenium.interactions.Actions;
import org.apache.commons.io.FileUtils;
import org.openqa.selenium.TakesScreenshot;
import org.openqa.selenium.firefox.FirefoxDriver;
import org.openqa.selenium.interactions.Actions;
import org.openqa.selenium.By;
import org.openqa.selenium.Keys;
import org.openqa.selenium.WebElement;
import org.testng.annotations.Test;
import org.openqa.selenium.*;

import java.awt.Rectangle;
import java.awt.Robot;
import java.awt.Toolkit;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;

import org.openqa.selenium.OutputType;

import com.thoughtworks.selenium.SeleneseTestNgHelper;

public class ckqhh 
{
    public static void main(String[] args)
    
    {
         System.setProperty("webdriver.firefox.bin","C:\\Program Files (x86)\\Mozilla Firefox\\firefox.exe");    //设置火狐的安装路径，防止系统找不到
            
         FirefoxDriver driver = new FirefoxDriver();        //初始化FireFox浏览器实例，并打开浏览器
         
        try
        {
             driver.manage().window().maximize();         //最大化窗口
             
             Thread.sleep(3000);        
             
             driver.manage().window().maximize();         //最大化窗口
             
             Thread.sleep(3000);


             driver.get("https://www.baidu.com");  
             
             Thread.sleep(1000);
             
             Actions action = new Actions(driver);
             
             action.moveToElement(driver.findElementByLinkText("设置")).perform();     //鼠标悬浮在 设置  元素上面
             
             driver.findElementByClassName("setpref").click();      // 打开搜索设置
             
             Thread.sleep(8000);
             
             

             List<WebElement> list = driver.findElements(By.xpath("//select[@id=‘nr‘]/*"));
             
             for (WebElement ele : list)
             {
           
                 if(ele.getAttribute("value").equals("50"))
                 {
                     ele.click();
                     break;
                 }
             }

             
             Thread.sleep(5000);
             
        }catch (Exception e) 
        {
            e.printStackTrace();
        }finally 
        {
            driver.quit();
        
         }
   }
    

}