Java中的继承和多态实现

我正在尝试实现继承和多态性的程序，但是我尝试了这个程序，但是该程序的问题是每次我编译此消息时都会弹出

编译错误-

/tmp/scodhvest/[email protected]/Main.java:5: error: cannot find symbol
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
^
symbol: class BufferedReader
location: class Main
/tmp/scodhvest/[email protected]/Main.java:5: error: cannot find symbol
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
^
symbol: class BufferedReader
location: class Main
/tmp/scodhvest/[email protected]/Main.java:5: error: cannot find symbol
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
^
symbol: class InputStreamReader
location: class Main
3 errors

这是主要的课程

public class Main {
public static void main(String args[])throws Exception{
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
int type,n;
System.out.println("Enter the number of transactions");
n=Integer.parseInt(br.readLine());
Account[] ac=new Account[n];
for(int i=0;i<n;i++){
    Account a=new Account();
System.out.println("Enter the account number");
a.setAccountNumber(br.readLine());
System.out.println("Enter the holder name");
a.setHolderName(br.readLine());
System.out.println("Enter the email address");
a.setEmail(br.readLine());
System.out.println("Enter the secret code");
a.setSecretCode(br.readLine());
System.out.println("Enter the number of debits");
a.setNumberOfDebits(Integer.parseInt(br.readLine()));
System.out.println("Enter the number of credits");
a.setNumberOfCredits(Integer.parseInt(br.readLine()));
ac[i]=a;
}
System.out.println("1)Generate Statement from account number\n"
        + "2)Generate Statement from secretcode and email\n"
        + "Enter your choice");
type=Integer.parseInt(br.readLine());
if(type>2||type<1){
    System.out.println("Invalid");
    System.exit(0);
}
switch(type){
case 1: 
    System.out.println("Enter the account number");
    Account account=new Account().generateStatement(ac,br.readLine());
    if(account==null)
        System.out.println("No account found from given match");
    else{
        System.out.println("Account Number :      "+account.getAccountNumber()+"\n"
                + "Holder Name : "+account.getHolderName()+"\n"
                + "Number of Debits : "+account.getNumberOfDebits()+"\n"
                + "Number of Credits : "+account.getNumberOfCredits());
    }
    break;
case 2:
    System.out.println("Enter the secret code");
    String code=br.readLine();
    System.out.println("Enter the email address");
    Account accnt=new Account().generateStatement(ac,code,br.readLine());
    if(accnt==null)
        System.out.println("No account found from given match");
    else{
        System.out.println("Account Number : "+accnt.getAccountNumber()+"\n"
                + "Holder Name : "+accnt.getHolderName()+"\n"
                + "Number of Debits : "+accnt.getNumberOfDebits()+"\n"
                + "Number of Credits : "+accnt.getNumberOfCredits());
    }
    break;
default:
    System.out.println("Invalid");
}

}
}