Hi, guys.
I have something which i can't understand the benefit when using prototype
pattern. On the book 'Sun Certified Enterprise Architect for
J2EE Tech..', the benefits of using prototype pattern is like that:
1. Adding and Removing products at run time.
2. Specifying new objects by varying value.
3. Specifying new objects by varying structure.
4. Reducing subclassing.
5. Configuring an application with classes dynamically.
i can know how the prototype pattern composed of. but i can't understand the benefit listings(2,3,4)
Is there anybody who can tell me the reason why the benefit is like that?
1.
package framework;
import java.util.*;
public class Manager {
private Hashtable showcase = new Hashtable();
public void register(
String name, Product proto) {
showcase.put(name, proto);
}
public Product create(String protoname) {
Product p = (Product)showcase.get(protoname);
return p.createClone();
}
}
2. package framework;
public interface Product extends Cloneable {
public abstract void use(String s);
public abstract Product createClone();
}
3.
import framework.*;
public class Main {
public static void main(String[] args) {
Manager manager = new Manager();
UnderlinePen upen = new UnderlinePen('~');
MessageBox mbox = new MessageBox('*');
MessageBox sbox = new MessageBox('/');
manager.register("strong message", upen);
manager.register("warning box", mbox);
manager.register("slash box", sbox);
Product p1 = manager.create("strong message");
p1.use("Hello, world.");
Product p2 = manager.create("warning box");
p2.use("Hello, world.");
Product p3 = manager.create("slash box");
p3.use("Hello, world.");
}
}
4.
import framework.*;
public class MessageBox implements Product {
private char decochar;
public MessageBox(char decochar) {
this.decochar = decochar;
}
public void use(String s) {
int length = s.getBytes().length;
for (int i = 0; i & lt; length + 4; i++) {
System.out.print(decochar);
}
System.out.println("");
System.out.println(decochar + " " + s + " " + decochar);
for (int i = 0; i & lt; length + 4; i++) {
System.out.print(decochar);
}
System.out.println("");
}
public Product createClone() {
Product p = null;
try {
p = (Product)clone();
} catch (CloneNotSupportedException e) {
e.printStackTrace();
}
return p;
}
}
5.
import framework.*;
public class UnderlinePen implements Product {
private char ulchar;
public UnderlinePen(char ulchar) {
this.ulchar = ulchar;
}
public void use(String s) {
int length = s.getBytes().length;
System.out.println("\"" + s + "\"");
System.out.print(" ");
for (int i = 0; i & lt; length; i++) {
System.out.print(ulchar);
}
System.out.println("");
}
public Product createClone() {
Product p = null;
try {
p = (Product)clone();
} catch (CloneNotSupportedException e) {
e.printStackTrace();
}
return p;
}
}
