A little bit a clarification with returning objects.

[Aziz]

In the following code:

Java:

private Element type; // . . . public Element getElement() {   return type; }

and later:

Java:

private Element typeOfElement; // . . . typeOfElement = getElement();

In my understanding, the 'getElement()' returns a pointer to the 'type' member, right? So, if something like changeType() is called on 'typeOfElement', does this change 'type' in the first code snippet? 'typeOfElement' and type point to the object, right? I want to make 'typeOfElement' a new object, but with all the same information as 'type'. Would I use the copy() method, or what?

[bugzpodder]

there are no pointers in java. all objects are pass by reference. to make another copy, either implement the copy constructor or override the clone method

[Aziz]

Okay, thought so, thank you for the clarification

[wtd]

Consider the following. I use Scala because it has an interactive interpreter and syntax I find nicer to work with than Java. The semantics remain relevant, though.

code:

scala> class A(private val b: java.util.ArrayList) { def getB = b } defined class A scala> val a = new A(new java.util.ArrayList) a: line15$object.A = line15$object$A@1ad0839 scala> val b = a getB b: java.util.ArrayList = [] scala> b add 42 line18: scala.Boolean = true scala> b line19: java.util.ArrayList = [42] scala> a getB line20: java.util.ArrayList = [42] scala>

[Aziz]

Yes, I see, and I actually understood that.

Anyways, another question.

Java:

public Element getType()     {         return type;     }         public void setType(Element type)     {         this.type = type;     }         public static void main(String[] args)     {         Weapon sword;         ElementalWeapon fireSword;                 sword = new Weapon("Sword", "A sword", 30, 10);         fireSword = new ElementalWeapon("Fire Sword",                 "A flaming hot sword", 70, 10, new FireElement());                 if (fireSword instanceof Elemental &&             fireSword.getType() instanceof FireElement)         {             System.out.println("This sword is elemental" +                                "and of the fire element");         }                    }

I want to be able to compare if the object is elemental, and if it is a ceratin type (ie FireElement) but I'm not sure if 'return type;' is safe, as anything else could change it. How would I implement a copy() or clone() method in Element, I've tried and no succes. The CloneNotSupportedException is throwing me off, even when I implement clone.

[wtd]

Can I see your other classes?

[wtd]

bugzpodder wrote:

there are no pointers in java. all objects are pass by reference.

Actually, it's worth noting that you have this exactly backwards.

In Java all Object type variables are handled by pointers. You just can't arbitrarily manipulate these pointers.

These pointers are then passed by value to methods.

Were they pass by reference, we could do something like:

code:

public class Test {    private static String testString = "Hello";    private static void test(String s) {       s = "world";    }    public static void main(String[] args) {       System.out.println(testString);       test(testString);       System.out.println(testString);    } }

[Aziz]

I've included the appropriate source files. Thanks wtd.

code:

package rpg.element; public class Element {        private String name;         public Element(String name)     {         this.name = name;     }         public String getName()     {         return name;     }         public String toString()     {         return name;     } }

code:

package rpg.item.weapon; import rpg.element.*; public class ElementalWeapon extends Weapon implements Elemental {     private Element type;     public ElementalWeapon(String name, String desc, int value, int damage, Element type)     {         super(name, desc, value, damage);                 this.type = type;     }         public Element getType()     {         return type;     }     public void setType(Element type)     {         this.type = type;     } public static void main(String[] args)     {         Weapon sword;         ElementalWeapon fireSword;                 sword = new Weapon("Sword", "A sword", 30, 10);         fireSword = new ElementalWeapon("Fire Sword",                 "A flaming hot sword", 70, 10, new FireElement());                 if (fireSword instanceof Elemental &&             fireSword.getType() instanceof FireElement)         {             System.out.println("This sword is elemental" +                                "and of the fire element");         }                    } }

code:

package rpg.element; import rpg.element.Element; public class FireElement extends Element {     public FireElement()     {         super("Fire");     } }

[wtd]

Well, one perhaps less than immediately relevant suggestion:

The methods in your Elkemental interface should probably be getElementType and setElementType.

I'll look more closely tomorrow.

[bugzpodder]

yes you are right wtd. in fact i think i've posted a site a while ago that explains this clearly than most others. it made two points which kind of amusing. cant find it though.