java多型-優化上個例項

開閉原則：對修改是封閉的，對擴充套件是開放的，不要違反開閉原則。

可以使用多型解決這個問題。父類的引用變數可以引用子類是物件。

寫的越是抽象，越是穩定

public class printerDemo {
	public static void main(String[] args) {
		/*colorPrinter cp = new colorPrinter("惠普");
		blackPrinter bp = new blackPrinter("聯想");*/
		printer p1 = new colorPrinter("惠普");
		printer p2 = new blackPrinter("聯想");
		printer p3 = new DDDPrinter("索尼");
		school sch = new school();
		/*sch.setBlackPrinter(bp);
		sch.setColorPrinter(cp);*/
		sch.setPriner(p1);
		sch.setPriner(p2);
		/*cp.print("abc");
		bp.print("abc");*/
		p1.print("hello");
		p2.print("hello");
		p3.print("hello");
	}
	
}

class school{
	/*private colorPrinter cp = null;
	private blackPrinter bp = null;*/
	private printer p = null;
	/*public void setColorPrinter(colorPrinter cp) {
		this.cp = cp;
	}
	public void setBlackPrinter(blackPrinter bp) {
		this.bp = bp;
	}*/
	public void setPriner(printer p) {
		this.p = p;
	}
	public void print(String content) {
		/*cp.print(content);
		bp.print(content);*/
		p.print(content);
	}
}

class printer{
	private String brand;
	public String getBrand() {
		return brand;
	}
	
	public printer(String brand) {
		this.brand = brand;
	}
	
	public void print(String content) {//重寫
		
	}
}

class colorPrinter extends printer{
	public colorPrinter(String brand) {
		super(brand);
	}
	
	public void print(String content) {
		System.out.println(getBrand()+"彩色列印："+content);
	}
}

class blackPrinter extends printer{
	public blackPrinter(String brand) {
		super(brand);
	}
	
	public void print(String content) {
		System.out.println(getBrand()+"黑白列印："+content);
	}
}

class DDDPrinter extends printer{
	public DDDPrinter(String brand) {
		super(brand);
	}
	
	public void print(String content) {
		System.out.println(getBrand()+"3D列印："+content);
	}
}