多态

最新推荐文章于 2025-08-05 17:20:40 发布

转载最新推荐文章于 2025-08-05 17:20:40 发布 · 55 阅读

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原文链接：https://my.oschina.net/u/3740271/blog/2051256

文章标签：

#python #java

2019独角兽企业重金招聘Python工程师标准>>>

package package1;

public class Demo11 {
public static void main(String[] args) {
	ColorPrinter color=new ColorPrinter("联想");
	BlackPrinter blck=new BlackPrinter("惠普");
	School stu=new School();
	//stu.setColorPrinter(color);
	stu.setBlackPrinter(blck);
	stu.print("hello java");
}
}
class Printer{
	private String brand;
	public Printer(String brand) {
		this.brand=brand;
	}
	public String getPrint() {
		return brand;
	}
	//此打印方法有子类来实现
	public void print(String content) {
		
	}
}
class ColorPrinter extends Printer{

	public ColorPrinter(String brand) {
		super(brand);
	}
	//对父类方法进行重写
	public void print(String content) {
			System.out.println(getPrint()+"彩色打印"+content);
	}
}
class BlackPrinter extends Printer{

	public BlackPrinter(String brand) {
		super(brand);
	}
	//对父类方法进行重写
	public void print(String content) {
			System.out.println(getPrint()+"黑白打印"+content);
	}
}
class School{
	private ColorPrinter cP=null;
	private BlackPrinter bP=null;
	//安装彩色打印机
	public void setColorPrinter(ColorPrinter cp) {
		this.cP=cp;
	}
	//安装黑白打印机
	public void setBlackPrinter(BlackPrinter bp) {
		this.bP=bp;
	}
	public void print(String content) {
		bP.print(content);
	}
}
以上是彩色打印机和黑白打印机的实现，如果在加入一台针式打印机那么又得进行添加一个类（针式打印机的类），而且在学校这个类中添加属性。如此一来不断的添加打印机不断添加类太麻烦，那么用多态来实现改进这一麻烦的过程。
package package1;

public class Demo11 {
public static void main(String[] args) {
	ColorPrinter color=new ColorPrinter("联想");
	BlackPrinter blck=new BlackPrinter("惠普");
	School stu=new School();
	//stu.setPrinter(color);
	stu.setPrinter(blck);
	stu.print("hello java");
}
}
class Printer{
	private String brand;
	public Printer(String brand) {
		this.brand=brand;
	}
	public String getPrint() {
		return brand;
	}
	//此打印方法有子类来实现
	public void print(String content) {
		
	}
}
class ColorPrinter extends Printer{

	public ColorPrinter(String brand) {
		super(brand);
	}
	//对父类方法进行重写
	public void print(String content) {
			System.out.println(getPrint()+"彩色打印"+content);
	}
}
class BlackPrinter extends Printer{

	public BlackPrinter(String brand) {
		super(brand);
	}
	//对父类方法进行重写
	public void print(String content) {
			System.out.println(getPrint()+"黑白打印"+content);
	}
}
class School{
	/*
	private ColorPrinter cP=null;
	private BlackPrinter bP=null;
	*/
	//改进后：直接写父类的引用变量(学校安装打印机)
	private Printer p=null;
	/*
	 * //安装彩色打印机
	public void setColorPrinter(ColorPrinter cp) {
		this.cP=cp;
	}
	//安装黑白打印机
	public void setBlackPrinter(BlackPrinter bp) {
		this.bP=bp;
	}*/
	
	//写一个通用的方法,拿父类的引用变量作为参数，好处就是可以接受任何其子类对象
	public void setPrinter(Printer p) {
		this.p=p;
	}
	public void print(String content) {
		p.print(content);
	}
}
通过多态使程序有更好的可维护性和扩展性

转载于:https://my.oschina.net/u/3740271/blog/2051256