Question

I was going through the Flyweight sample code at http://www.oodesign.com/flyweight-pattern-wargame-example-java-sourcecode.html and wondering how it really works when we assign a static instance (SOLDIER as in the above site) to a non-static soldier instance in SoldierClient do we really reduce the object size since each SoldierClient will somehow hold a copy of SOLDIER instance in each SoldierClient object we create?

EDIT:

In the method moveSoldier()
it says

// delete soldier representation from previous location
// then render soldier representation in new location

How come this doesn’t affect all the objects created in class WarGame

package flyweight;

public class SoldierImp implements Soldier {

    /**
     * Intrinsic State maintained by flyweight implementation
     * Solider Shape ( graphical represetation)
     * how to display the soldier is up to the flyweight implementation
     */
    private Object soldierGraphicalRepresentation;

    /**
     * Note that this method accepts soldier location 
     * Soldier Location is Extrinsic and no reference to previous location 
     * or new location is maintained inside the flyweight implementation
     */
    public void moveSoldier(int previousLocationX, int previousLocationY,
            int newLocationX, int newLocationY) {

        // delete soldier representation from previous location 
        // then render soldier representation in new location   
    }

Answer 1

A SoldierClient doesn’t hold a copy of SOLDIER, it holds a reference to SOLDIER, and every SoldierClient holds a reference to the same SOLDIER.

Answering the edit

Each soldier’s location is held in SoldierClient instances (currentLocationX and currentLocationY properties). The code comments for those properties spell it out as well: “this state is maintained by the client” (i.e., “this state is not maintained in the SoldierImp instance”).

Everything is in moveSoldier‘s parameters: there’s no SoldierImp instance state. Think of it like a static utility method. Coordinates are provided by the SoldierClient instance; they’re never stored by the SoldierImp–just used.