为什么我不能在类中声明字符串？

Question

public class Account {

    public int pin;
    public int accountnumber;
    public string accounttype;
    public double balance;
}

It tells me string cannot be resolved as a type.

Answer 1

它是大写的S String

Answer 2

Try

public String accounttype;

The others ( int , double ) are so called primitive data types where String is like Account "just another class".
int has an "equivalent" (yeah, I know) ( Integer ), that is like String

Answer 3

String is not a primitive type. In Java, objects/classes naming convention would have the first letter capitalized.

You know it is an object because it has methods and it is basically an array of characters.

Also you should declare most Class member variables as private (or protected) unless there is a specific reason you need to make it public.