命令窗口下，编译出现ArrayList提示字符串出错的问题

在命令窗口下编译，会出现ArrayList提示字符串出错的问题：

import java.util.ArrayList;

import java.util.Random;

public class Emperor{

private static int maxNumOfEmperor = 2; //最多只能有连个皇帝

//皇帝叫什么名字

private static ArrayList emperorInfoList = new ArrayList(maxNumOfEmperor); //装皇帝的列表

private static ArrayList emperorList = new ArrayList(maxNumOfEmperor);

private static int countNumOfEmperor = 0; //正在被人尊称的是那个皇帝

//先把2个皇帝产生出来

static{

//把所有的皇帝都产生出来

for(int i=0; i<maxNumOfEmperor;i++){

emperorList.add(new Emperor("皇"+(i+1)+"帝"));

}

}

private Emperor(){

}

private Emperor(String info){

emperorInfoList.add(info);

}

public static Emperor getInstance(){

Random Random = new Random();

countNumOfEmperor = Random.nextInt(maxNumOfEmperor);

return (Emperor)emperorList.get(countNumOfEmperor);

}

public static void emperorInfo(){

System.out.println("我就是皇帝" + emperorInfoList.get(countNumOfEmperor));

}

}

public class Minister{

public static void main(String agrs[]){

/*

Emperor emperor1 = Emperor.getInstance();

emperor1.emperorInfo();

Emperor emperor2 = Emperor.getInstance();

emperor2.emperorInfo();

*/

int ministerNum = 10;

for(int i=0; i<ministerNum; i++){

Emperor emperor = Emperor.getInstance();

System.out.println("第"+(i+1)+"个大臣参拜的是：");

emperor.emperorInfo();

}

}

}

如果不导入

import java.util.ArrayList;

import java.util.Random;

包名的话，用命令行窗口编译会报错，

private static ArrayList emperorInfoList = new ArrayList(maxNumOfEmperor);

private static ArrayList emperorList = new ArrayList(maxNumOfEmperor);

会提示找不到ArrayList 和Random这个字符串。