等

public class HospitalSystem {

//门诊挂号
public void register(){

    //实现门诊挂号逻辑

}

//门诊收费
public void charge(){

    //实现门诊收费逻辑

}

//门诊退费
public void refund(){

    //实现门诊退费逻辑

} 

//发票打印
public void printInvoice(){

    //实现发票打印逻辑                                       

}
}