Inheritance in Java

[Angela Jessi]

Hi,
I want to know following:
I have three classes.
Parent.class
child1.class
child2.class
Public class Parent extends Applet{
public void init()
{
child1 c1 = new child1();
child2 c2 = new child2()
}
}
public class child1
{
public void send()
{
x = a+b;
}
}

public class child2
{
public void getValue()
{
QUESTION: I want to access the value of x?
How can i access without calling send()?
}
}
QUESTION: I want to access the value of x in child2.class,getValue() method without calling send() of child1.class?

And also if i import child1.class in child2.class. DID I have make reference to child1.class in child2.class?
Please let me know
Thanks in advance,
angela

[Bruce Wingate]

I have three classes.
Parent.class
child1.class
child2.class

These classes are not parent and children based on your definitions below.

public class child1
{
public void send()
{
x = a+b;
}
}

public class child2
{
public void getValue()
{
QUESTION: I want to access the value of x?
How can i access without calling send()?
}
}
QUESTION: I want to access the value of x in child2.class,getValue() method without calling send() of child1.class?

x is a local variable to the send() method. After the method runs, it is "out of scope" and essentially disappears. You could declare x as a public variable in the class, then you could just reference it via by saying c1.x. *BUT* child2 would have to have a reference to the child1 variable.

And also if i import child1.class in child2.class. DID I have make reference to child1.class in child2.class?

As the program stands now, you don't need to import either one. If you were to reference child1 inside of child2, then you would have to import child1. If you don't reference child2 inside of child1, then you don't have to import it. (Someone correct me if I'm wrong, because I'm not positive on this.)

[Cindy Glass]

They way you have it written now, x is a local variable to the send() method, and will not exist outside of it, even in the Child1 class. They ways to make it available include:
put a return type on the send() method and return x. Then Child 2 can make an instance of Child1 and call it's send method.

   public class Child1 extends Parent
                {
       public int send()
                {
                int x = a+b;
                return x;
           }
       }
//Then in Child 2 you put:
      Child1 kid = new Child1();
      int i = kid.send();

Or you can declare the x in the class (not the method), then you can access it directly

    public class Child1 extends Parent
       {
       int y = this.send();
       public int send()
                {
                int x = a+b;
                return x;
           }
       }
//Then in Child2
     Child1 kid = new Child1();
     int i = kid.y;     

The last way is if x is a static variable of the class

    public class Child1 extend Parent
       {
       static int y = whatever;
       public int send()
                {
                int x = a+b;
                return x;
           }
       }
//Then in Child2
//     You don't need an instance to reference a static variable
     int i = Child1.y;     
// Of course if you want to have the send() method involved it would need to be a static method also.

[This message has been edited by Cindy Glass (edited February 23, 2001).]