设计模式之适配器模式与装饰者模式

知识来源极客学院

适配器模式的基本原理

现实生活例子，香港插头与内地插座，使用适配器使得香港插头可以与内地插座连接。

代码示例；

public interface HKPlugs {
	public void output();
}
class SmallHKPlugs implements HKPlugs{
	@Override
	public void output() {
		System.out.println("Small HongKong Plugs!");
	}
}
public interface MLPlugs {
	public void output();
}
class SmallMLPlugs implements MLPlugs{
	@Override
	public void output() {
		System.out.println("Small Mainland Plugs!");
	}
}
public class MLPlugsAdapter implements HKPlugs {
	private MLPlugs mlPlugs;
	public MLPlugsAdapter(MLPlugs mlPlugs){
		this.mlPlugs=mlPlugs;
	}
	@Override
	public void output(){
		mlPlugs.output();
	}
}
public class Test {
	public static void main(String[] args) {
		HKPlugs mlPlugs=new MLPlugsAdapter(new SmallMLPlugs());
		mlPlugs.output();
	}
}

output
Small Mainland Plugs!

对象适配器与类适配器

类适配器

public class MLPlugsAdapter extends SmallMLPlugs implements HKPlugs {
	@Override
	public void output(){
		super.output();
	}
}
public class Test {
	public static void main(String[] args) {
		HKPlugs mlPlugs=new MLPlugsAdapter();
		mlPlugs.output();
	}
}

output
Small Mainland Plugs!

从枚举器到迭代器的适配

public class EnumerationIterator implements Iterator<Object> {
	private Enumeration enumeration;
	public EnumerationIterator(Enumeration enumeration) {
		this.enumeration=enumeration;
	}
	@Override
	public boolean hasNext() {
		return enumeration.hasMoreElements();
	}

	@Override
	public Object next() {
		return enumeration.nextElement();
	}
	public void remove(){
		throw new UnsupportedOperationException();
	}
}

装饰者模式

装饰者模式原理

一、咖啡厅订单系统项目

装饰者模式示例演示

public abstract class Drink {
	public String description="";
	private float price=0f;
	public String getDescription() {
		return description+"-"+this.getPrice();
	}
	public void setDescription(String description) {
		this.description = description;
	}
	public float getPrice() {
		return price;
	}
	public void setPrice(float price) {
		this.price = price;
	}
	public abstract float cost();
}
public class Coffee extends Drink{
	@Override
	public float cost(){
		return super.getPrice();
	}
}
public class Decaf extends Coffee{
	public Decaf() {
		super.setDescription("Decaf");
		super.setPrice(3.0f);
	}
}
public class Espresso extends Coffee {
	public Espresso() {
		super.setDescription("Espresso");
		super.setPrice(4.0f);
	}
}
public class Decorator extends Drink {
	private Drink obj;
	public Decorator(Drink obj) {
		this.obj=obj;
	}
	@Override
	public float cost() {
		return super.getPrice()+obj.cost();
	}
	public String getDescription(){
		return super.description+"-"+super.getPrice()+"&&"+obj.getDescription();
	}
}
public class Chocolate extends Decorator {
	public Chocolate(Drink obj) {
		super(obj);
		super.setDescription("Chocolate");
		super.setPrice(3.0f);
	}

}
public class Milk extends Decorator {
	public Milk(Drink obj){
		super(obj);
		super.setDescription("Milk");
		super.setPrice(2.0f);
	}
}
public class CoffeeBar {
	public static void main(String[] args) {
		Drink order=new Decaf();
		System.out.println(order.cost());
		System.out.println(order.getDescription());
		order=new Milk(order);
		order=new Chocolate(order);
		System.out.println(order.getPrice());
		System.out.println(order.getDescription());
	}
}

output

3.0
Decaf-3.0
3.0
Chocolate-3.0&&Milk-2.0&&Decaf-3.0

装饰者模式介绍

Java内置装饰者

编写自己的Java I/O装饰者

public class UpperCaseInputStream extends FilterInputStream {

	protected UpperCaseInputStream(InputStream in) {
		super(in);
	}
	public int read() throws IOException{
		int c=super.read();
		return c==-1?c:Character.toUpperCase((char)c);
	}
	public int read(byte[]b,int offset,int len) throws IOException{
		int result=super.read(b, offset, len);
		for(int i=0;i<result;i++){
			b[i]=(byte)Character.toUpperCase((char)b[i]);
		}
		return result;
	}
}

public class InputTest {
	public static void main(String[] args) {
		int c;
		try {
			InputStream in=new UpperCaseInputStream(new BufferedInputStream(new FileInputStream("E:\\test.txt")));
			while((c=in.read())>=0){
				System.out.print((char)c);
			}
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
}

output

SAHIUDSHAIUHISDHAUIH