commandfactory.java

来自「Java 议程管理系统。使用GoF设计模式进行系统设计」· Java 代码 · 共 76 行

/**
 * 
 */
package agenda.ctrl;

import java.util.*;

import agenda.cmd.Command;

/**
 * class definition for command factory
 * 
 * @author Cyberpet
 * 
 */
public class CommandFactory {
	private HashMap<String, Command> cmdTable = new HashMap<String, Command>();

	/*
	 * add command into the hashmap
	 */
	public boolean addCmd(Command cmd) {
		if (cmd != null)
			return this.cmdTable.put(cmd.getName(), cmd) != null;
		else
			return false;
	}

	/*
	 * get command by name
	 */
	public Command getCmdByName(String name) {
		return this.cmdTable.get(name);
	}

	public String toString() {
		String res = new String();
		Collection<Command> Col = this.cmdTable.values();
		for (Command cmd : Col)
			res += cmd.toString();
		return res;
	}

	/**
	 * static class for Singleton design pattern, instance of CommandFactory
	 * will be created when the first time you make a call to
	 * CommandFactory.getInstance
	 * 
	 * @author Cyberpet
	 * @see CommandFactory#getInstance()
	 */
	static class CommandFactorySingletonHolder {
		static CommandFactory instance = new CommandFactory();
	}

	/**
	 * get the only instance of CommandFactory
	 * 
	 * @return CommandFactory
	 * @see CommandFactory
	 */
	public static CommandFactory getInstance() {
		return CommandFactorySingletonHolder.instance;
	}

	/**
	 * @param args
	 * @return void
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub

	}

}