打印机有黑白的，有彩色的，学校都有打印机，用于打印，现在用多态来描述

package jiCheng_duoTai;

//public class DaYinJi {
//  public static void main(String[] args) {
//    School s = new School();
//    BlackPrinter bp = new BlackPrinter("惠普牌");
//    ColorPrinter cp = new ColorPrinter("三星牌");
//    s.usePrinter(bp,"武汉大学");//打印的内容
//    s.usePrinter(cp,"软件技术二班");//打印的内容
//  }
//}
class Printer{//父类，打印机
 private String brand;


public Printer() {}
 public Printer(String brand) {
  this.brand = brand;
 }
 public void print(String content) {
  System.out.println(content);
 }
 public String getBrand() {
  return brand;
 }
 public void setBrand(String brand) {
  this.brand = brand;
 }
}
class BlackPrinter extends Printer {//子类，黑白打印机
 public BlackPrinter() {
  super();
 }
 public BlackPrinter(String brand) {
  super(brand);
 }
 public void print (String content) {
  System.out.println(getBrand()+"黑白打印机："+content);
 }
}
class ColorPrinter extends Printer{//子类，彩色打印机
 public ColorPrinter() {
  super();
 }
 public ColorPrinter(String brand) {
  super(brand);
 }
 public void print (String content) {
  System.out.println(getBrand()+"彩色打印机："+content);
  }
}
//class School{
// public void usePrinter(BlackPrinter bp,String content) {
//  bp.print(content);
// }
//  public void usePrinter(ColorPrinter cp,String content) {
//  cp.print(content);
// }
//}



//首先，上面的代码未使用到多态的形式，如果打印机的品牌很多，上面的代码就不适用了，所以进行改进，改为多态形式
//首先将上面的School类进行注释，进行新的编写
class School{
 public void usePrinter(Printer p,String content) {
  p.print(content);
 }
}
//其次，将main函数代码块进行注释，进行重新的编写，进而实现多态
public class DaYinJi {
 public static void main(String[] args) {
   School s = new School();
   Printer p1=new BlackPrinter("惠普牌");
   Printer p2=new ColorPrinter("三星牌");
   s.usePrinter(p1,"武汉大学");
   s.usePrinter(p2,"软件技术专业");
 }
}
//对于上面的代码也可以改用下面的这个形式
//School s = new School();
//BlackPrinter bp = new BlackPrinter("惠普牌");
//ColorPrinter cp = new ColorPrinter("三星牌");
//s.usePrinter(bp,"武汉大学");//父类引用指向子类对象  p=bp;
//s.usePrinter(cp,"软件技术二班");