我想在自己的类中调用一个抽象类的方法。抽象类是:publicabstractclassCall{publicConnectiongetEarliestConnection(){Connectionearliest=null;...returnearliest;}}我想调用上面的方法，调用类是:publicclassMyActivityextendsActivity{Connectionc=newConnection();privatevoidgetCallFailedString(Callcal){c=cal.getEarliestConnection();if(c==null){Sy