java 无法在初始化程序中引用静态枚举字段？
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Cannot refer to the static enum field within an initializer?
提问by IAdapter
I just got Java5 project that has this error, i tried using Java5 and Java6, but its still there. it worked somehow before(since it was in svn), how can i bypass that compiler error?
我刚刚收到出现此错误的 Java5 项目，我尝试使用 Java5 和 Java6，但它仍然存在。它以前以某种方式工作（因为它在 svn 中），我如何绕过该编译器错误？
回答by Jon Skeet
Don't "bypass" the error - it won't do what you want it to. The error is there for good reason.
不要“绕过”错误 - 它不会做你想要的。错误是有充分理由的。
The enum values are initialized before any other static fields. If you want to do something like adding all the values into a map, do it in a static initializer aftereverything else:
枚举值在任何其他静态字段之前初始化。如果你想要做的事，如添加的所有值到一个地图，做一个静态初始化后一切：
import java.util.*;
public enum Foo
{
BAR, BAZ;
private static final Map<String, Foo> lowerCaseMap;
static
{
lowerCaseMap = new HashMap<String, Foo>();
for (Foo foo : EnumSet.allOf(Foo.class))
{
// Yes, use some appropriate locale in production code :)
lowerCaseMap.put(foo.name().toLowerCase(), foo);
}
}
}
回答by Luan Nico
Another way to "bypass" it, if you need for example a counter or something that needs to run on each initalization, is to create a private static inner class, like so:
“绕过”它的另一种方法，例如，如果您需要一个计数器或需要在每次初始化时运行的东西，则创建一个私有静态内部类，如下所示：
public enum Foo {
BAR, BAZ;
private static final class StaticFields {
private static final Map<String, Foo> lowerCaseMap = new HashMap<>();
private static int COUNTER = 0;
}
private Foo() {
StaticFields.lowerCaseMap.put(this.name().toLowerCase(), this);
StaticFields.COUNTER++;
}
}
