I was Going through an example of flyweight Pattern i found online.
import java.util.Random;
import java.util.HashMap;
// A common interface for all players
interface Player
{
public void assignWeapon(String weapon);
public void mission();
}
// Terrorist must have weapon and mission
class Terrorist implements Player
{
// Intrinsic Attribute
private final String TASK;
// Extrinsic Attribute
private String weapon;
public Terrorist()
{
TASK = "PLANT A BOMB";
}
public void assignWeapon(String weapon)
{
// Assign a weapon
this.weapon = weapon;
}
public void mission()
{
//Work on the Mission
System.out.println("Terrorist with weapon "
+ weapon + "|" + " Task is " + TASK);
}
}
// CounterTerrorist must have weapon and mission
class CounterTerrorist implements Player
{
// Intrinsic Attribute
private final String TASK;
// Extrinsic Attribute
private String weapon;
public CounterTerrorist()
{
TASK = "DIFFUSE BOMB";
}
public void assignWeapon(String weapon)
{
this.weapon = weapon;
}
public void mission()
{
System.out.println("Counter Terrorist with weapon "
+ weapon + "|" + " Task is " + TASK);
}
}
// Claass used to get a playeer using HashMap (Returns
// an existing player if a player of given type exists.
// Else creates a new player and returns it.
class PlayerFactory
{
/* HashMap stores the reference to the object
of Terrorist(TS) or CounterTerrorist(CT). */
private static HashMap <String, Player> hm =
new HashMap<String, Player>();
// Method to get a player
public static Player getPlayer(String type)
{
Player p = null;
/* If an object for TS or CT has already been
created simply return its reference */
if (hm.containsKey(type))
p = hm.get(type);
else
{
/* create an object of TS/CT */
switch(type)
{
case "Terrorist":
System.out.println("Terrorist Created");
p = new Terrorist();
break;
case "CounterTerrorist":
System.out.println("Counter Terrorist Created");
p = new CounterTerrorist();
break;
default :
System.out.println("Unreachable code!");
}
// Once created insert it into the HashMap
hm.put(type, p);
}
return p;
}
}
// Driver class
public class CounterStrike
{
// All player types and weopons (used by getRandPlayerType()
// and getRandWeapon()
private static String[] playerType =
{"Terrorist", "CounterTerrorist"};
private static String[] weapons =
{"AK-47", "Maverick", "Gut Knife", "Desert Eagle"};
// Driver code
public static void main(String args[])
{
/* Assume that we have a total of 10 players
in the game. */
for (int i = 0; i < 10; i++)
{
/* getPlayer() is called simply using the class
name since the method is a static one */
Player p = PlayerFactory.getPlayer(getRandPlayerType());
/* Assign a weapon chosen randomly uniformly
from the weapon array */
p.assignWeapon(getRandWeapon());
// Send this player on a mission
p.mission();
}
}
// Utility methods to get a random player type and
// weapon
public static String getRandPlayerType()
{
Random r = new Random();
// Will return an integer between [0,2)
int randInt = r.nextInt(playerType.length);
// return the player stored at index 'randInt'
return playerType[randInt];
}
public static String getRandWeapon()
{
Random r = new Random();
// Will return an integer between [0,5)
int randInt = r.nextInt(weapons.length);
// Return the weapon stored at index 'randInt'
return weapons[randInt];
}
}
Implementation : This implement the creation of Terrorists and Counter Terrorists In the game of Counter Strike. So we have 2 classes one for Terrorist(T) and other for Counter Terrorist(CT). Whenever a player asks for a weapon we assign him the asked weapon. In the mission, terrorist’s task is to plant a bomb while the counter terrorists have to diffuse the bomb.
I believe This example is wrong.In this code Object remains the same, we are only changing the weapon, if a new Player enters the game, everyone weapon's will changed. Am i understanding this right?. Can anyone Provide me a good example of Fly Weight.
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