Structural Patterns Part 1/7: Adapter Pattern

Structural Patterns Part 1/7: Adapter Pattern

目录

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Definition

Adapter Pattern是连接两个互不兼容或者互相独立的类或接口的桥梁。

一个现实中的例子就是读卡器，连接电脑和内存卡。读卡器就是Adapter，内存卡就是Adaptee，电脑就是Client了。

一句话(英文更好理解):
A class extends another class, takes in an object, and makes the taken object behave like the extended class.

何时使用？当希望连接两个互不兼容或者互相独立的类或接口时。

使用频率： Medium High

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UML Class Diagram

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Implementation

读卡器负责读卡，光驱负责读光盘。

// Reader.java
package designpatternsstructuralpatterns.adapter;

public interface Reader {
    void read();
}

// ReaderImpl.java
package designpatternsstructuralpatterns.adapter;

class CardReader implements Reader {    
    Card card;

    public CardReader(Card card) {
        this.card = card;
    }

    @Override
    public void read() {
        card.dataOutPut();
    }   
}

class DiskReader implements Reader {    
    Disk disk;

    public DiskReader(Disk disk) {
        this.disk = disk;
    }

    @Override
    public void read() {
        disk.dataOutPut();
    }   
}

class Card {
    void dataOutPut() {
        System.out.println("Card::DATA");
    }
}

class Disk {
    void dataOutPut() {
        System.out.println("Disk::DATA");
    }
}

// AdapterDemo.java
package designpatternsstructuralpatterns.adapter;

public class AdapterDemo {
    public static void main(String[] args) {
        Computer computer = new Computer();
        computer.read(new CardReader(new Card()));
        computer.read(new DiskReader(new Disk()));
    }
}

class Computer {
    public void read(Reader reader) {
        reader.read();
    }
}

// output
Card::DATA
Disk::DATA