今天花了點時間看了物件導向分析與設計，看了前四章的感覺是，這本書花了很多時間在指導我們如何分析客戶的需求，如何寫出良好的 user cases ，當然對於程式的封裝也有稍微提及。
不過今天要介紹的是UML圖
UML
是系統分析以及設計的重要產物，也是實作以及測試的依據。
下面這張圖是 head first 物件導向分析與設計裡面的一個 sample，
使用者希望能有一個 Remote 能夠在按下按鈕的時候， DogDoor 會打開/關閉，
然後也希望家裡的狗 Bark 的時候， DogDoor 可以 Recognize 是自己家的狗然後開門。
上圖中 Remote -> DogDoor 之間的數字 1 代表著
Remote has 1 個 DogDoor
相同的 BarkRecognizer also has 1個 DogDoor
DogDoor has n 個 Bark 而DogDoor 可以在 allowedBarks的屬性裡儲存任意數量的Bark
看完了UML圖以及解釋之後接下來就是實作部分
Sample Code
Bark.java
public class Bark {
/**
* @param args
*/
private String sound;
public Bark(String sound)
{
this.sound = sound;
}
public String getSound()
{
return sound;
}
public boolean equals(Bark bark)
{
if(bark.getSound().equals(this.sound))
return true;
return false;
}
}
BarkRecognizer.java
public class BarkRecognizer {
/**
* @param args
*/
private DogDoor door;
public BarkRecognizer(DogDoor door)
{
this.door = door;
}
public void recognize(Bark bark)
{
java.util.List<Bark> allowedBarks = door.getAllowedBarks();
for (Bark allowedBark : allowedBarks) {
if(bark.equals(allowedBark))
{
door.Open();
return;
}
}
System.out.println("Door is not Open");
}
}
DogDoor.java
public class DogDoor {
/**
* @param args
*/
private List<Bark> allowedBarks = new ArrayList<Bark>();
private boolean Open=false;
public void Open()
{
System.out.println("Door Open");
final Timer timer = new Timer();
timer.schedule(new TimerTask(){
@Override
public void run() {
// TODO Auto-generated method stub
Close();
timer.cancel();
}
},5000);
}
public void Close()
{
System.out.println("Door Close");
}
public boolean IsOpen()
{
return Open;
}
public void addAllowedBark(Bark bark)
{
allowedBarks.add(bark);
}
public List<Bark> getAllowedBarks()
{
return allowedBarks;
}
}
Remote.java
public class Remote {
/**
* @param args
*/
private DogDoor door;
public Remote(DogDoor door)
{
this.door = door;
}
public void pressButton()
{
if(door.IsOpen())
door.Close();
door.Open();
}
}
接著拿出head first 裡面所提供的測試檔案
Test
public static void main(String[] args) {
// TODO Auto-generated method stub
DogDoor door = new DogDoor();
door.addAllowedBark(new Bark("rowlf"));
door.addAllowedBark(new Bark("rooowlf"));
door.addAllowedBark(new Bark("rawlf"));
door.addAllowedBark(new Bark("woof"));
BarkRecognizer recognizer = new BarkRecognizer(door);
Remote remote = new Remote(door);
System.out.println("Bruce starts barking.");
recognizer.recognize(new Bark("rowlf"));
System.out.println("Bruce has gone outside...");
try{
Thread.currentThread().sleep(6000);
}catch(InterruptedException ex)
{
}
System.out.println("Bruce's all done...");
System.out.println("but he's stuck outside...");
Bark smallDogBark = new Bark("open the door");
System.out.println("A small dog starts barking.");
recognizer.recognize(smallDogBark);
System.out.println("Bruce starts barking");
recognizer.recognize(new Bark("rowlf"));
System.out.println("Bruce's Back inside");
}
Result
Bruce starts barking.
Door Open
Bruce has gone outside...
Door Close
Bruce's all done...
but he's stuck outside...
A small dog starts barking.
Door is not Open
Bruce starts barking
Door Open
Bruce's Back inside
Door Close
結論
這次展示了如何從UML 到程式的coding
UML就有點像是蓋房子之前的藍圖，
有了藍圖就可以降低user想蓋巴黎鐵塔結果developer卻蓋出金字塔的問題。
我想這對user 來說應該也算是一大福音吧 XD
