[英]How to create a generic class in what I can call an Enum.valueOf() in Java?
所以我有這些課程:
public class DeviceInState implements MyInterface<Device> {
private List<DeviceState> toStates(String statesString) {
List<String> states = Lists.newArrayList(statesString.split(","));
return states.stream().map(DeviceState::valueOf).collect(Collectors.toList());
}
}
public class DeviceHistoryInState implements MyInterface<DeviceHistory> {
private List<EventType> toStates(String statesString) {
List<String> states = Lists.newArrayList(statesString.split(","));
return states.stream().map(EventType::valueOf).collect(Collectors.toList());
}
}
這些枚舉:
public enum EventType{
NEW("N"), ACTIVE("A"), INACTIVE("I");
}
public enum DeviceState{
REGISTRATED("R"), SUSPENDED("S"), DELETED("D");
}
區別在於:
DeviceInState implements MyInterface<Device>
; 但DeviceHistoryInState implements MyInterface<DeviceHistory>
DeviceState::valueOf
在DeviceInState
被調用; 但EventTypes::valueOf
在DeviceHistoryInState
被調用
我有幾個這樣的其他類,所以我想制作一個通用的類。 但我不知道這是否可能。 我如何以一種可以調用::valueOf
方法的方式參數化我的類或方法?
提前致謝。
這就是我要做的……
public interface State< E extends Enum< E > > { … }
然后我的enums
會實現......
…
public enum DeviceState implements State< DeviceState > { … }
…
public enum EventType implements State< EventType > { … }
…
„ ……其實這些方法都沒有被覆蓋。 這些方法只是從被覆蓋的方法中調用…… ”
考慮到您使用@Overrides
注釋了代碼段中的方法,我發現這是一個非常令人困惑的評論。 為了讓我自己不那么困惑,我的實驗性實現確實覆蓋了一些東西......
public class DeviceInState extends ToStateable< DeviceState > implements Specification< Device > {
@Override
public List< DeviceState > toStates( String statesString ) {
List< String > states = asList( statesString.split( "," ) );
return states.stream( ).map( String::trim ).map( DeviceState::valueOf ).collect(Collectors.toList());
}
}
我能夠成功地稱之為......
…
ToStateable< DeviceState > deviceToStateable = new DeviceInState( );
List< DeviceState > deviceStates = deviceToStateable.toStates( "SUSPENDED,REGISTERED,DELETED" );
ToStateable< EventType > eventToStateable = new DeviceHistoryInState( );
List< EventType > eventTypes = eventToStateable.toStates( "INACTIVE, NEW, ACTIVE" );
…
打印出我能看到的那些物體……
[SUSPENDED, REGISTERED, DELETED]
[INACTIVE, NEW, ACTIVE]
SUSPENDED
EXPERIMENT SUCCESSFUL
您可以在 DeviceHistoryInState 和 DeviceInState 中刪除兩個類似的toState()
實現,並定義一個適用於任何枚舉類型的通用方法:
static <E extends Enum<E>> List<E> toStates(Class<E> cls, String statesString) {
List<String> states = Arrays.asList(statesString.split(","));
return states.stream().map(String::trim).map(s -> Enum.valueOf(cls, s))
.collect(Collectors.toList());
}
但是有一個小成本:您必須將 EnumType.class 作為參數傳遞,但這相當簡單:
List< DeviceState > devStates = toStates(DeviceState.class, "SUSPENDED,REGISTRATED,DELETED");
=> [SUSPENDED, REGISTRATED, DELETED]
List< EventType > evTypes = toStates(EventType.class, "INACTIVE,NEW,ACTIVE");
=> [INACTIVE, NEW, ACTIVE]
或者,您可以對調用上述內容的 EventType.toState(String) 進行簡單定義。
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