ArrayList not recognizing subclass variables

Question

I am having a problem with seeing subclass attributes in an ArrayList.

Here's some snippets of the main parts of my code that matter here.

private ArrayList<Person> people = new ArrayList<Person>;

abstract class Person {
String fName;
String lName;
}

public class Employee extends Person {
protected int empID;
}

public class Client extends Person {
protected int clientID;
}

When using a for loop to search by clientID, I am getting

Enterprise.java:134: cannot find symbol symbol : variable clientID location: class Person

I have tried with and without instanceof Client on the for loop. I have also tried using Client instead of Person in the for loop parameters.

for(Person x : people) {
if(x.clientID == cid) {
    System.out.println(x);
}

Before turning these into subclasses I had them in an ArrayList of their own kind and everything worked flawlessly.

Any help would be greatly appreciated!

Are you sure your list of people only contains Client instances? If not you will get errors. I also don't see how the code your posted would compile unless you cast x to Client before attempting the x.clientID.. something like ((Client)x).clientID == cid — Mike Dinescu
– Mike Dinescu, Commented Nov 1, 2011 at 20:57

thejh · Accepted Answer · 2011-11-01 20:56:38Z

4

You have to either put them in a seperate list or cast them:

for (Person person : people) {
  if (person instanceof Client) {
    Client client = (Client) person;
    if (client.clientID == cid) {
      System.out.println("found!");
    }
  }
}

answered Nov 1, 2011 at 20:56

thejh

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1 Comment

Paul Stutes Over a year ago

Thank you very much! I am not sure how I forgot that. Went over that in detail about two weeks ago.

Mechkov · Accepted Answer · 2011-11-01 20:56:04Z

0

You are using Private instance variables. There are NOT visible anywhere outside their own class. Change to protected or public inst. variables and should fix the issue.

Also this code

x.clientID == cid

is looking for instance variable in the Person abstract class, and since there is no such variable you get the compiler error.

Regards!

answered Nov 1, 2011 at 20:56

Mechkov

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2 Comments

Paul Stutes Over a year ago

I'm sorry, those are actually meant to be listed as protected, overlooked that when I typed up the question. Edited OP as well.

Mechkov Over a year ago

You also have to worry about whether the inst. variables are part of your class. X.clientID wont work, since Person class does not have cliendID is not part of it.

kgautron · Accepted Answer · 2011-11-01 20:57:54Z

0

You need to cast the Person as a Client :

((Client) x).clientId;

answered Nov 1, 2011 at 20:57

kgautron

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Comments

Heisenbug · Accepted Answer · 2011-11-01 20:59:40Z

0

The point is that clientID property doesn't belong to parent class Person. Use instanceof this way in order to downcast the object:

for(Person x : people) {
    if (x instanceof Client){
         Client c = (Client) x;
         if(c.clientID == cid) {
             System.out.println(x);
         }
}

Even if that is possible, it is often a signal that you have a design problem. Probably you need to refactor your code, for example storing different subclass of Person into different ArrayList.

answered Nov 1, 2011 at 20:59

Heisenbug

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