user.java

设计模式代码

//
public class User{
	//
	private Calculator calculator=new Calculator();
	//
	private ArrayList commands=new ArrayList[];
	//
	private int current=0;
	//
	//
	public void Redo(int levels){
		System.out.println("------Redo levels:"+levels);
		//
		for(int i=0;i<levels;i++){
			if(current<commands.length()-1)
			    ((Command)commamds[current++]).Execute();
		}
	}
	
	//
	public void Undo(int levels){
		System.out.println("------Undo levels:"+levels);
		//
		for(int i=0;i<levels;i++){
			if(current>0)
			    ((Command)commands[--current]).UnExecute();
		}
	}
	
	//
	public void Compute(char operator,int operand){
		//
		Command command=new CalculatorCommand(calculator,operator,opeand);
		//
		command.Execute();
		//
		command.Add(command);
		current++;
	}
}