commandlist.java

来自「《JAVA与模式》附书中源代码」· Java 代码 · 共 52 行

package com.javapatterns.command.drawapplet;

import java.util.Stack;

public class CommandList
{
    private	Stack executedCommands = new Stack();
    private	Stack unexecutedCommands = new Stack();

	private void _execute( Command command )
    {
        command.execute();
        executedCommands.push( command );
    }

	public void execute( Command command )
	{
        unexecutedCommands.removeAllElements();
        _execute( command );
    }

	public void unexecute()
	{
        Command command = (Command)executedCommands.pop();
        command.unexecute();
        unexecutedCommands.push( command );
    }

	public void reexecute()
	{
        Command command = (Command)unexecutedCommands.pop();
        _execute( command );
    }

	public void reset()
	{
        executedCommands.removeAllElements();
        unexecutedCommands.removeAllElements();
    }

    public boolean canUnexecuteCommand()
    {
        return !executedCommands.empty();
    }

    public boolean canReexecuteCommand()
    {
        return !unexecutedCommands.empty();
    }
}