命令模式实现简单计算器功能包括撤销

package Command; import java.util.ArrayList; public class Calculator { private CommandInterface addcommand = null; private CommandInterface subcommand = null; private ArrayList<CommandInterface> undoCommand = new ArrayList<CommandInterface>(); public void setaddcommand(CommandInterface addcommand) { this.addcommand = addcommand; } public void setsubcommand(CommandInterface subcommand) { this.subcommand = subcommand; } public void addPressed() { this.addcommand.Execute(); undoCommand.add(this.addcommand); } public void subPressed() { this.subcommand.Execute(); undoCommand.add(this.subcommand); } public void undoImpl() { if(this.undoCommand.size()>0) { System.out.println("可撤销的命令为"+this.undoCommand.size()); CommandInterface command = this.undoCommand.get(undoCommand.size()-1); command.Undo(); this.undoCommand.remove(command); } else { System.out.println("可撤销的命令为"+this.undoCommand.size()); } } }