Mega Code Archive
Command pattern
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/*
Software Architecture Design Patterns in Java
by Partha Kuchana
Auerbach Publications
*/
import java.util.HashMap;
public class CommandTest {
public static void main(String[] args) {
//Add an item to the CD category
//create Receiver objects
Item CD = new Item("A Beautiful Mind");
Category catCD = new Category("CD");
//create the command object
CommandInterface command = new AddCommand(CD, catCD);
//create the invoker
ItemManager manager = new ItemManager();
//configure the invoker
//with the command object
manager.setCommand(command);
manager.process();
//Add an item to the CD category
CD = new Item("Duet");
catCD = new Category("CD");
command = new AddCommand(CD, catCD);
manager.setCommand(command);
manager.process();
//Add an item to the New Releases category
CD = new Item("Duet");
catCD = new Category("New Releases");
command = new AddCommand(CD, catCD);
manager.setCommand(command);
manager.process();
//Delete an item from the New Releases category
command = new DeleteCommand(CD, catCD);
manager.setCommand(command);
manager.process();
}
}
class ItemManager {
CommandInterface command;
public void setCommand(CommandInterface c) {
command = c;
}
public void process() {
command.execute();
}
}
class Item {
private HashMap categories;
private String desc;
public Item(String s) {
desc = s;
categories = new HashMap();
}
public String getDesc() {
return desc;
}
public void add(Category cat) {
categories.put(cat.getDesc(), cat);
}
public void delete(Category cat) {
categories.remove(cat.getDesc());
}
}
class DeleteCommand implements CommandInterface {
Item item;
Category cat;
public DeleteCommand(Item i, Category c) {
item = i;
cat = c;
}
public void execute() {
item.delete(cat);
cat.delete(item);
}
}
interface CommandInterface {
public void execute();
}
class Category {
private HashMap items;
private String desc;
public Category(String s) {
desc = s;
items = new HashMap();
}
public String getDesc() {
return desc;
}
public void add(Item i) {
items.put(i.getDesc(), i);
System.out.println("Item '" + i.getDesc() + "' has been added to the '"
+ getDesc() + "' Category ");
}
public void delete(Item i) {
items.remove(i.getDesc());
System.out.println("Item '" + i.getDesc()
+ "' has been deleted from the '" + getDesc() + "' Category ");
}
}
class AddCommand implements CommandInterface {
Item item;
Category cat;
public AddCommand(Item i, Category c) {
item = i;
cat = c;
}
public void execute() {
item.add(cat);
cat.add(item);
}
}
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