Java Templates

[llee]

I've defined a class that has the following body:
class Condition {
...
ArrayList<? extends Condition> subconditions;
...
Condition (..., ArrayList <? extends Condition> subconditions) {
...
}
...
}
I also have a function that contains the following lines:
...
Condition condition = new Condition (..., new ArrayList<Condition> ());
...
Condition subcondition = DatabaseParser.parseConditionElement (...)
condition.subconditions.add (subcondition);
...

I'm getting the following error when I try to compile the above source code.

[javac] Compiling 18 source files to /home/llee/projects/android_app_projects/options/bin/classes
[javac] /home/llee/projects/android_app_projects/options/src/org/k4health/Ace/DatabaseParser.java:82: cannot find symbol
[javac] symbol : method add(org.k4health.Ace.Condition)
[javac] location: class java.util.ArrayList<capture#548 of ? extends org.k4health.Ace.Condition>
[javac] condition.subconditions.add (subcondition);
[javac] ^
[javac] Note: Some input files use unchecked or unsafe operations.
[javac] Note: Recompile with -Xlint:unchecked for details.
[javac] 1 error

I'm inexperienced with Java templates and do not know what this error message means. Any help would be greatly appreciated.

[Norm]

cannot find symbol
symbol : method add(org.k4health.Ace.Condition)

The compiler can not find an add() method that takes a org.k4health.Ace.Condition class object as a parameter.
Where is this method defined?

[llee]

The compiler can not find an add() method that takes a org.k4health.Ace.Condition class object as a parameter.
Where is this method defined?

The add method should belong to the ArrayList class. condition.subconditions should be an ArrayList.

[Norm]

Can you make a small complete program that shows the errors?

[llee]

package org.k4health.Ace;

import java.io.Serializable;
import java.util.ArrayList;

// Represents medical conditions.
public class Condition implements Serializable {
  ArrayList<? extends Condition> subconditions; 

  Condition (ArrayList<? extends Condition> subconditions) {
    this.subconditions = subconditions;
  }
}

public class DatabaseParser {
 static Condition parseConditionElement (Element conditionElem) {
    Condition condition = new Condition (
      new ArrayList<Condition> ()
    );
    Condition subcondition = new Condition (new ArrayList<Condition> ());
    condition.subconditions.add (subcondition); // Compiler error occurs here. 
    return condition;
  }
}