command.java

面向对象的设计思想

import java.io.Serializable;

public abstract class Command implements Serializable {
  protected Object    result = null;
  protected Exception excep = null;

  protected abstract void execute(DrawModel broker);
    public Object getResult( )  throws  Exception{
    if (this.result != null){
      return this.result;
    }
    if (this.excep != null){
      throw this.excep;
    }
    return null;
  }
}