假设我有一个枚举
public enum Blah {
A, B, C, D
}
我想找到一个字符串的枚举值,例如“a”,它将是Blah.a。如何做到这一点?
Enum.valueOf()是我需要的方法吗?如果是,我将如何使用它?
假设我有一个枚举
public enum Blah {
A, B, C, D
}
我想找到一个字符串的枚举值,例如“a”,它将是Blah.a。如何做到这一点?
Enum.valueOf()是我需要的方法吗?如果是,我将如何使用它?
当前回答
使用Joshua Bloch《有效Java:
(为简洁起见简化)
enum MyEnum {
ENUM_1("A"),
ENUM_2("B");
private String name;
private static final Map<String,MyEnum> ENUM_MAP;
MyEnum (String name) {
this.name = name;
}
public String getName() {
return this.name;
}
// Build an immutable map of String name to enum pairs.
// Any Map impl can be used.
static {
Map<String,MyEnum> map = new ConcurrentHashMap<String, MyEnum>();
for (MyEnum instance : MyEnum.values()) {
map.put(instance.getName().toLowerCase(),instance);
}
ENUM_MAP = Collections.unmodifiableMap(map);
}
public static MyEnum get (String name) {
return ENUM_MAP.get(name.toLowerCase());
}
}
另请参见:
使用枚举和实例映射的Oracle Java示例
枚举类型中静态块的执行顺序
如何从Java枚举的String值查找它
其他回答
使用Joshua Bloch《有效Java:
(为简洁起见简化)
enum MyEnum {
ENUM_1("A"),
ENUM_2("B");
private String name;
private static final Map<String,MyEnum> ENUM_MAP;
MyEnum (String name) {
this.name = name;
}
public String getName() {
return this.name;
}
// Build an immutable map of String name to enum pairs.
// Any Map impl can be used.
static {
Map<String,MyEnum> map = new ConcurrentHashMap<String, MyEnum>();
for (MyEnum instance : MyEnum.values()) {
map.put(instance.getName().toLowerCase(),instance);
}
ENUM_MAP = Collections.unmodifiableMap(map);
}
public static MyEnum get (String name) {
return ENUM_MAP.get(name.toLowerCase());
}
}
另请参见:
使用枚举和实例映射的Oracle Java示例
枚举类型中静态块的执行顺序
如何从Java枚举的String值查找它
枚举非常有用。我一直在使用Enum为不同语言的某些字段添加描述,如以下示例:
public enum Status {
ACT(new String[] { "Accepted", "مقبول" }),
REJ(new String[] { "Rejected", "مرفوض" }),
PND(new String[] { "Pending", "في الانتظار" }),
ERR(new String[] { "Error", "خطأ" }),
SNT(new String[] { "Sent", "أرسلت" });
private String[] status;
public String getDescription(String lang) {
return lang.equals("en") ? status[0] : status[1];
}
Status(String[] status) {
this.status = status;
}
}
然后,您可以根据传递给getDescription(Stringlang)方法的语言代码动态检索描述,例如:
String statusDescription = Status.valueOf("ACT").getDescription("en");
这里有一个方法可以对任何Enum执行此操作,并且不区分大小写。
/**
* Finds the value of the given enumeration by name, case-insensitive.
* Throws an IllegalArgumentException if no match is found.
**/
public static <T extends Enum<T>> T valueOfIgnoreCase(
Class<T> enumeration, String name) {
for (T enumValue : enumeration.getEnumConstants()) {
if (enumValue.name().equalsIgnoreCase(name)) {
return enumValue;
}
}
throw new IllegalArgumentException(String.format(
"There is no value with name '%s' in Enum %s",
name, enumeration.getName()
));
}
public enum DivisionType {
DEFAULT(0){
@Override
public void sort(List<SigInUserDto> SigInUserDtos) {
SigInUserDtos.sort(new SigInUserCoinsQueueComparator());
}
},
ASSIGNPOINTS(1) {
@Override
public void sort(List<SigInUserDto> SigInUserDtos) {
SigInUserDtos.sort(new SigInUserPointsComparator());
}
},
ASSIGNEVENORDER(2) {
@Override
public void sort(List<SigInUserDto> SigInUserDtos) {
SigInUserDtos.sort(new SigInUserOrderCountComparator());
}
};
public final Integer label;
DivisionType(Integer label) {
this.label = label;
}
public static DivisionType getTypeById(Integer id) {
for (DivisionType value : DivisionType.values()) {
if (value.label == id) {
return value;
}
}
return DEFAULT;
}
public abstract void sort(List<SigInUserDto> SigInUserDtos);
}
使用枚举:DivisionType.getTypeById(object.getBalancingTypesId().intValue()).sort(sigInUserDtoList);
在这里,sort()函数在每个枚举匹配下实现(重载)。因此,基于对象“object.getBalancingTypesId().intValue()”匹配值,调用并排序特定的枚举匹配。
public enum ToggleStatusUpdate {
OFF("off", 1),
ON("on", 2);
private final String name;
private final int position;
private ToggleStatusUpdate(String name, int position) {
this.name = name;
this.position = position;
}
public String getName() {
return name;
}
public int getPosition() {
return position;
}
public static int getPositionForName(String name) {
for(ToggleStatusUpdate toggleStatusUpdate : ToggleStatusUpdate.values()) {
if (toggleStatusUpdate.getName().equals(name)) {
return toggleStatusUpdate.getPosition();
}
}
return -1;
}
public static void main(String[] args) {
System.out.println(ToggleStatusUpdate.getPositionForName("off"));
}
}