一般如果是用string做值的enum,比較直接是寫在interface
---------------------
interface PlayserStatus {
public final static String PLAY="play";
public final static String STOP="stop";
}
class Player {
String _status;
Player(String status){
_status=status;
}
....
....
}
然後再用
var player=new Player(PlayserStatus.PLAY);
---------------------
問題是這樣就無法限制Player的建構元一定是要在PLAY/STOP這樣的範圍,太危險了
所以還是enum寫法比較安全
--------------.
enum PlayerStatus {
AXN_INIT("init"),
AXN_PLAY("Play"),
AXN_PAUSE("Pause"),
AXN_FINISH("Finshed");
private final String value;
private PlayerStatus(String s) {
value = s;
}
public String toString(){
return value;
}
}
class Player {
private PlayerStatus xntStatus;
public Player(PlayerStatus status) {
xntStatus=status;
}
@Override public void setStatus(PlayerStatus s) {
xntStatus=s;
}
@Override public String getStatus() {
return xntStatus.toString();
}
}
....
...
public void main(String[] args){
...
...
...
var player=new Player(PlayerStatus.AXN_INIT);
System.out.println("status is "+player.getStatus());
player.setStatus(PlayerStatus.AXN_PLAY);
System.out.println("status is "+player.getStatus());
....
}
----------------------------------------------------
這樣就可以更具體限制了
有關java enum 類型的更完整的介紹,請參考以下更精闢的好文
https://tpu.thinkpower.com.tw/tpu/articleDetails/1432
同場加映!!
如果是要切換狀態時的行為,不是在player裡大改, 而是由playerStatus決定呢?
------------原班人馬,加個狀態表------------------------------
//先定義行為
interface PlayerIsDoing{
void doing();
}
class InitPlayer implements PlayerIsDoing{
public void doing(){
System.out.println("Doing Init Now");
}
}
class PlayingPlayer implements PlayerIsDoing{
public void doing(){
System.out.println("Playing Now");
}
}
//再定義行為對映表,順便了解一下直接給值的HashMap的寫法
class HtLolder{
static PlayerIsDoing p1=new InitPlayer();
static PlayerIsDoing p2=new PlayingPlayer();
static Map<String,PlayerIsDoing> ht=new HashMap<String,PlayerIsDoing>(){
{
put("init",p1);
put("Play",p2);
}
};
}
//改一下enum類別
enum PlayerStatus {
AXN_INIT("init"),
AXN_PLAY("Play");
Map<String,PlayerIsDoing> ht=HtLolder.ht;
private final String value;
private PlayerStatus(String s) {
value = s;
}
public String toString(){
return value;
}
//重點來了!!
public void doPlaying(){
ht.get(value).doing(); <-----------
}
}
class Player implements PlayerAction{
private PlayerStatus xntStatus;
public Player(PlayerStatus status) {
xntStatus=status;
}
@Override public void setStatus(PlayerStatus s) {
xntStatus=s;
}
@Override public String getStatus() {
xntStatus.doPlaying();<-----------
return xntStatus.toString();
}
}
//it's show time!!
public static void main(String[] args) throws IOException {
var player=new Player(PlayerStatus.AXN_INIT);
System.out.println("status is "+player.getStatus());
player.setStatus(PlayerStatus.AXN_PLAY);
System.out.println("status is "+player.getStatus());
...
....
}
--------------------------------------------------------------
這樣,有新行為,player不用改(小改啦),把新行為放在PlayerStatus跟行為對映表所在的套件中
會比較靈活些吧
大家加油吧!!
