一、代码

/*
正常，不用多态写
class School{

public CaiSeDayin cy;
public HeBaiDayin hy;

public void anZhuang(CaiSeDayin cy){
    this.cy = cy;
}
public void anZhuangh(HeBaiDayin hy){
    this.hy = hy;
}

public void print(String contex){
    cy.print(contex);
}

}
*/

//多态写法，这样添加打印机就添加一个Dayin的子类就可以了
class School{

public Dayin dayinji;

public void anZhuang(Dayin dayinji){
    this.dayinji = dayinji;
}
public void print(String contex){
    dayinji.print(contex);
}

}

class Dayin{

public String pinpai;
public void print(String contex){}

}

class CaiSeDayin extends Dayin{

public void print(String contex){
    System.out.println("彩色打印机打印" + contex);
}

}

class HeBaiDayin extends Dayin{

public void print(String contex){
    System.out.println("黑白打印机打印" + contex);
}

}

class ZhenDayin extends Dayin{

public void print(String contex){
    System.out.println("针打印机打印" + contex);
}

}

public class Printor {

public static void main(String[] args) {
    /*正常，不用多态写
    School s = new School();
    CaiSeDayin c = new CaiSeDayin();
    s.anZhuang(c);
    s.print("xiao");
    
    HeBaiDayin h = new HeBaiDayin();
    s.anZhuangh(h);
    s.print("wei");
    */
    
    School s = new School();
    CaiSeDayin c = new CaiSeDayin();
    s.anZhuang(c);
    s.print("xiao");
    
    HeBaiDayin h = new HeBaiDayin();
    s.anZhuang(h);
    s.print("wei");
    
    ZhenDayin z = new ZhenDayin();
    s.anZhuang(z);
    s.print("小伟");
}

}

/*
彩色打印机打印xiao
黑白打印机打印wei
针打印机打印小伟
*/