我可以在 Java 中设置枚举起始值吗？
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Can I set enum start value in Java?
提问by qrtt1
I use the enum to make a few constants:
我使用枚举来创建一些常量：
enum ids {OPEN, CLOSE};
the OPEN value is zero, but I want it as 100. Is it possible?
OPEN 值为零，但我希望它为 100。这可能吗？
采纳答案by lavinio
Java enums are not like C or C++ enums, which are really just labels for integers.
Java 枚举不像 C 或 C++ 枚举，它们实际上只是整数的标签。
Java enums are implemented more like classes - and they can even have multiple attributes.
Java 枚举的实现更像类——它们甚至可以有多个属性。
public enum Ids {
OPEN(100), CLOSE(200);
private final int id;
Ids(int id) { this.id = id; }
public int getValue() { return id; }
}
The big difference is that they are type-safewhich means you don't have to worry about assigning a COLOR enum to a SIZE variable.
最大的区别在于它们是类型安全的，这意味着您不必担心将 COLOR 枚举分配给 SIZE 变量。
See http://docs.oracle.com/javase/tutorial/java/javaOO/enum.htmlfor more.
有关更多信息，请参阅http://docs.oracle.com/javase/tutorial/java/javaOO/enum.html。
回答by Paul Morie
Yes. You can pass the numerical values to the constructor for the enum, like so:
是的。您可以将数值传递给枚举的构造函数，如下所示：
enum Ids {
OPEN(100),
CLOSE(200);
private int value;
private Ids(int value) {
this.value = value;
}
public int getValue() {
return value;
}
}
See the Sun Java Language Guidefor more information.
有关详细信息，请参阅Sun Java 语言指南。
回答by serdar
If you use very big enum types then, following can be useful;
如果您使用非常大的枚举类型，那么以下可能很有用；
public enum deneme {
UPDATE, UPDATE_FAILED;
private static Map<Integer, deneme> ss = new TreeMap<Integer,deneme>();
private static final int START_VALUE = 100;
private int value;
static {
for(int i=0;i<values().length;i++)
{
values()[i].value = START_VALUE + i;
ss.put(values()[i].value, values()[i]);
}
}
public static deneme fromInt(int i) {
return ss.get(i);
}
public int value() {
return value;
}
}
回答by Maher Abuthraa
whats about using this way:
如何使用这种方式：
public enum HL_COLORS{
YELLOW,
ORANGE;
public int getColorValue() {
switch (this) {
case YELLOW:
return 0xffffff00;
case ORANGE:
return 0xffffa500;
default://YELLOW
return 0xffffff00;
}
}
}
there is only one method ..
只有一种方法..
you can use static method and pass the Enum as parameter like:
您可以使用静态方法并将枚举作为参数传递，例如：
public enum HL_COLORS{
YELLOW,
ORANGE;
public static int getColorValue(HL_COLORS hl) {
switch (hl) {
case YELLOW:
return 0xffffff00;
case ORANGE:
return 0xffffa500;
default://YELLOW
return 0xffffff00;
}
}
Note that these two ways use less memory and more process units .. I don't say this is the best way but its just another approach.
请注意，这两种方式使用更少的内存和更多的处理单元。我不是说这是最好的方式，而只是另一种方式。
回答by ggrandes
If you want emulate enum of C/C++ (base num and nexts incrementals):
如果您想模拟 C/C++ 的枚举（基本 num 和 nexts 增量）：
enum ids {
OPEN, CLOSE;
//
private static final int BASE_ORDINAL = 100;
public int getCode() {
return ordinal() + BASE_ORDINAL;
}
};
public class TestEnum {
public static void main (String... args){
for (ids i : new ids[] { ids.OPEN, ids.CLOSE }) {
System.out.println(i.toString() + " " +
i.ordinal() + " " +
i.getCode());
}
}
}
OPEN 0 100 CLOSE 1 101
OPEN 0 100 CLOSE 1 101
回答by maharvey67
The ordinal() function returns the relative position of the identifier in the enum. You can use this to obtain automatic indexing with an offset, as with a C-style enum.
ordinal() 函数返回标识符在枚举中的相对位置。您可以使用它来获取带有偏移量的自动索引，就像使用 C 样式枚举一样。
Example:
例子：
public class TestEnum {
enum ids {
OPEN,
CLOSE,
OTHER;
public final int value = 100 + ordinal();
};
public static void main(String arg[]) {
System.out.println("OPEN: " + ids.OPEN.value);
System.out.println("CLOSE: " + ids.CLOSE.value);
System.out.println("OTHER: " + ids.OTHER.value);
}
};
Gives the output:
给出输出：
OPEN: 100
CLOSE: 101
OTHER: 102
Edit: just realized this is very similar to ggrandes' answer, but I will leave it here because it is very clean and about as close as you can get to a C style enum.
编辑：刚刚意识到这与ggrandes 的答案非常相似，但我将其留在这里，因为它非常干净，并且与 C 风格的枚举尽可能接近。
回答by Gibbs
public class MyClass {
public static void main(String args[]) {
Ids id1 = Ids.OPEN;
System.out.println(id1.getValue());
}
}
enum Ids {
OPEN(100), CLOSE(200);
private final int id;
Ids(int id) { this.id = id; }
public int getValue() { return id; }
}
@scottf, You probably confused because of the constructor defined in the ENUM.
@scottf，您可能因为 ENUM 中定义的构造函数而感到困惑。
Let me explain that.
让我解释一下。
When class loaderloads enumclass, then enumconstructor also called. On what!! Yes, It's called on OPENand close. With what values 100for OPENand 200for close
当class loader加载enum类时，enum构造函数也被调用。什么！！是的，它被称为OPEN和close。有什么价值100为OPEN和200为close
Can I have different value?
我可以有不同的价值吗？
Yes,
是的，
public class MyClass {
public static void main(String args[]) {
Ids id1 = Ids.OPEN;
id1.setValue(2);
System.out.println(id1.getValue());
}
}
enum Ids {
OPEN(100), CLOSE(200);
private int id;
Ids(int id) { this.id = id; }
public int getValue() { return id; }
public void setValue(int value) { id = value; }
}
But, It's bad practice. enumis used for representing constantslike days of week, colors in rainbowi.e such small group of predefined constants.
但是，这是不好的做法。enum用于表示constantslike days of week，colors in rainbow即这样一小组预定义的常量。
回答by sperling
@scottf
@scottf
An enum is like a Singleton. The JVM creates the instance.
枚举就像单例。JVM 创建实例。
If you would create it by yourself with classes it could be look like that
如果你自己用类创建它，它可能看起来像这样
public static class MyEnum {
final public static MyEnum ONE;
final public static MyEnum TWO;
static {
ONE = new MyEnum("1");
TWO = new MyEnum("2");
}
final String enumValue;
private MyEnum(String value){
enumValue = value;
}
@Override
public String toString(){
return enumValue;
}
}
And could be used like that:
并且可以这样使用：
public class HelloWorld{
public static class MyEnum {
final public static MyEnum ONE;
final public static MyEnum TWO;
static {
ONE = new MyEnum("1");
TWO = new MyEnum("2");
}
final String enumValue;
private MyEnum(String value){
enumValue = value;
}
@Override
public String toString(){
return enumValue;
}
}
public static void main(String []args){
System.out.println(MyEnum.ONE);
System.out.println(MyEnum.TWO);
System.out.println(MyEnum.ONE == MyEnum.ONE);
System.out.println("Hello World");
}
}
回答by Coristat
I think you're confused from looking at C++ enumerators. Java enumerators are different.
我认为您对 C++ 枚举器感到困惑。Java 枚举器是不同的。
This would be the code if you are used to C/C++ enums:
如果您习惯于 C/C++ 枚举，这将是代码：
public class TestEnum {
enum ids {
OPEN,
CLOSE,
OTHER;
public final int value = 100 + ordinal();
};
public static void main(String arg[]) {
System.out.println("OPEN: " + ids.OPEN.value);
System.out.println("CLOSE: " + ids.CLOSE.value);
System.out.println("OTHER: " + ids.OTHER.value);
}
};
