Java-在方法中传递数组，无法识别变量

Question

I have been stuck on this one for days, but I have broken it down here. What I need to do is to create an array of accounts with about 9 variables each (AccountID, WithdrawlDates, etc.) that the user can input in a command prompt. From the createAccount() method I can send an instance of user and a accountNum, but the user is not recognized on the receiving setAccount method.

Here's the code:

class User{

   private int accountID;

   User( int id )
   {
       accountID = id;
   }

   static void setAccountID(User user[], int accountNum)
   {       
       user.accountID = accountNum; //accountID is not recognized here
   }
   static void getAccountID(User user){System.out.println(user.accountID);}
   }

class TestUser
{
   public static void main(String[] args)
   {       
      createAccount();
   }

   static void createAccount(){
       User[] user = new User[2];
       user[0] = new User(25);
       User.setAccountID(user, 2001); 
   }
}

I am open to changing the flow of this, but I don't know where to start.

Thanks!

Answer 1

There's no reason to pass an array of User objects. Try this instead:

class User{

   private int accountID;

   User( int id )
   {
       accountID = id;
   }

   static void setAccountID(User user, int accountNum)
   {       
       user.accountID = accountNum; //accountID is not recognized here
   }
   static void getAccountID(User user){System.out.println(user.accountID);}
   }

class TestUser
{
   public static void main(String[] args)
   {       
      createAccount();
   }

   static void createAccount(){
       User user = new User(25);
       User.setAccountID(user, 2001); 
   }
}

EDIT: If you need to maintain an array of users as @Luiggi Mendoza suggests in his comment, just pass a single array element to setAccountID() :

static void createAccount(){
   User[] user = new User[2];
   user[0] = new User(25);
   User.setAccountID(user[0], 2001); // set id for first User
}

Answer 2

To access the elements of an array instead of doing something with the array itself you use square brackets like so:

user[userIndex]

from there you can either change the element like this

user[userIndex] = new User(id);

or access/modify something about the element itself like this

user[userIndex].accountID = whatever;

Additionally, your use of static in the setAccountID is confusing things. A static method cannot know anything about accountID because accountID is a part of a uniquely created object where the static method belongs to the class, and not any particular object. If it must be static for some reason, you will need to change the method to look something like this

static void setAccountID(User user[], int userIndex, int accountNum)
{       
   user[userIndex].accountID = accountNum;
}

but the following would be much better, since you know the user inside the array anyway:

void setAccountID(int accountNum)
{       
   this.accountID = accountNum;
}

called like this:

user[userIndex].setAccountID(accountNum);