which classes to write..how to program this?

11. Create a class called Families which creates a one-to-many mapping of parent name (String) to Child objects. Create any needed member variables and write the two specified methods.

class Families {


public void addToFamily( String parent, Child child) {


}

public List<Child> getChildren( String parent) {


}
}

Thanks for posting your assignment. I assume that you are going to show the fruits of your efforts and then ask a direct question, correct?

Any exception text?

Quote:

---

Originally Posted by sony1

11. Create a class called Families which creates a one-to-many mapping of parent name (String) to Child objects. Create any needed member variables and write the two specified methods.

class Families {


public void addToFamily( String parent, Child child) {


}

public List<Child> getChildren( String parent) {


}
}

---

mapping maybe you need a HashMap ?? just a thought

import java.util.HashMap;
import java.util.List;

class Families {

HashMap<String,List<String>> hm=new HashMap<String,List<String>>();

void find(String parent,String child)
{

List<String> l = hm.get(parent);
if(l.isEmpty()== true)
{
List list = null;
list.add(child);
hm.put(parent, list);
}

else
{
// parent already exists
l.add(child);
}
}
//public void addToFamily( String parent, Child child)
//{
//a=find(parent);

//}


public List<String> getChildren( String parent)
{
List l=null;
l=hm.get(parent);
return l;
}

public static void main(String args[])
{Families ob=new Families();

ob.find("nav","khushi");
ob.find("nav", "soni");
ob.find("nav", "vish");
ob.find("ash", "sonu");
List li=null;

li=ob.getChildren("naveen");
System.out.println(li);



}
}

Quote:

---

Originally Posted by sony1

Code:

---

import java.util.HashMap;
import java.util.List;

class Families {
       
        HashMap<String,List<String>> hm=new HashMap<String,List<String>>();

        void find(String parent,String child)
        {
               
        List<String> l = hm.get(parent);
        if(l.isEmpty()== true)

---

---

What if 'parent' isn't present (yet) in your map? Most certainly 'l' will be null.

kind regards,

Jos

how to get rid of this error then?
also the question was this..
i m suppose to vreate parent child mapping
how m i suppose to cretae the parent and child class?
this is not an assignment question as pointed out by the moderator.
It was asked in one of the interviews..and i ws nt able to answer it.


class Families {



public void addToFamily( String parent, Child child) {



}

public List<Child> getChildren( String parent) {


}
}

Your design should allow for a person NOT to have children.
And when creating a child, the parents MUST be given to the Child's Constructor.