justHelloWorld :
In this question and this post is explained how to clone objects with final fields by using protected copy constructors.
However, supposing that we have:
public abstract class Person implements Cloneable
{
private final Brain brain; // brain is final since I do not want
// any transplant on it once created!
private int age;
public Person(Brain aBrain, int theAge)
{
brain = aBrain;
age = theAge;
}
protected Person(Person another)
{
Brain refBrain = null;
try
{
refBrain = (Brain) another.brain.clone();
// You can set the brain in the constructor
}
catch(CloneNotSupportedException e) {}
brain = refBrain;
age = another.age;
}
public String toString()
{
return "This is person with " + brain;
// Not meant to sound rude as it reads!
}
public Object clone()
{
return new Person(this);
}
public abstract void Think(); //!!!!
…
}
Returns an error since we can't instantiate an abstract class. How can we solve this?
Eran :
You don't implement the clone()
method in the abstract class, only in the concrete sub-classes.
public class SomeConcretePerson extends Person
{
public SomeConcretePerson (SomeConcretePerson another)
{
super (another); // this will invoke Person's copy constructor
}
public Object clone()
{
return new SomeConcretePerson(this);
}
}
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