在 Java 方法中使用标志的最佳实践
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Best practice of using flags in Java method
提问by Roalt
What's the best practice for specifying flags in a Java method?
在 Java 方法中指定标志的最佳实践是什么？
I've seen SWT using int as bitfields, like:
我见过 SWT 使用 int 作为位域，例如：
(example partially from "Effective Java, 2nd Ed." page 159):
（部分示例来自“Effective Java，第二版”第 159 页）：
public class Text {
public static final int STYLE_BOLD = 1 << 0; // 1
public static final int STYLE_ITALIC = 1 << 1; // 2
void printText(String text, int flags) {
}
}
and your client call looks like:
你的客户电话看起来像：
printText("hello", Text.STYLE_BOLD | Text.STYLE_ITALIC);
..but this is discouraged as you can mixed flags (int values) from different classes together without any compiler checks.
..但这是不鼓励的，因为您可以将来自不同类的标志（int 值）混合在一起，而无需任何编译器检查。
In the same book ("Effective Java"), I see the use of EnumSet, but then your user call becomes:
在同一本书（“Effective Java”）中，我看到了 EnumSet 的使用，但随后您的用户调用变为：
printText("hello", EnumSet.of(Style.Bold, Style.ITALIC));
I find this a bit verbose and I prefer the elegance of SWT.
我觉得这有点冗长，我更喜欢 SWT 的优雅。
Is there any other alternative or is this basically the two tastes you must pick?
有没有其他选择，或者这基本上是您必须选择的两种口味？
采纳答案by Aravindan R
Guess you have hit a wall. I don't see any other option. Java is verbose that's a fact. In situations like this i usually add a local variable to make the code more readable. You can do this,
估计你撞墙了。我看不到任何其他选择。Java 很冗长，这是事实。在这种情况下，我通常会添加一个局部变量以使代码更具可读性。你可以这样做，
EnumSet<Style> styles = EnumSet.of(Style.Bold, Style.ITALIC);
printText("hello", styles);
回答by Edwin Buck
If you want bit style flags, Java wraps them in a BitSet. It's been around for ages, yet few people bother to use it (preferring embedding C style bit handling in ints).
如果您需要位样式标志，Java 会将它们包装在BitSet. 它已经存在了很长时间，但很少有人愿意使用它（更喜欢在整数中嵌入 C 风格的位处理）。
The api for BitSet can be found here.
Coupled with a few well chosen static ints, it does pretty well until you start getting into checking and setting multiple bits in one pass.
再加上一些精心挑选的静态整数，它会做得很好，直到您开始一次检查和设置多个位。
回答by missingfaktor
I advise that you go with the EnumSetapproach.
我建议你采用这种EnumSet方法。
EnumSet<Style> styles = EnumSet.of(Style.Bold, Style.Italic);
This approach provides better type safety, and Stylebeing an enum will have full-blown OO capabilities.
这种方法提供了更好的类型安全性，并且Style作为枚举将具有全面的 OO 功能。
回答by bertvanbrakel
Late answer for anyone coming across this. Here is one way to do it to reduce memory and have a nice enum like api:
任何遇到此问题的人的迟到答案。这是一种减少内存并拥有像 api 这样的漂亮枚举的方法：
public static class MyFlag {
public static final MyFlag A = new MyFlag(1<<0);
public static final MyFlag B = new MyFlag(1<<1);
public static final MyFlag C = new MyFlag(1<<2);
public static final MyFlag ALL = A.and(B).and(C);
private final int flag;
private MyFlag(int flag){
this.flag = flag;
}
public MyFlag and(MyFlag limit){
return new MyFlag(flag & limit.flag);
}
public MyFlag not(MyFlag limit){
return new MyFlag(flag | ~limit.flag);
}
public boolean isSet(MyFlag limit){
if(limit ==null){
return false;
}
return (this.flag & limit.flag) != 0;
}
}
method:
方法：
public void doFoo(MyFlag flag){
if(MyFlag.A.isSet(flag)){
....
}
if(MyFlag.C.isSet(flag)){
....
}
}
call:
称呼：
x.doFoo(MyFlag.A.and(MyFlag.C));
回答by John Hart
If you only have a limited number of methods that will be taking a set of styles (like printText, in your example), you can tweak their signature to take a variable number of Style params:
如果您只有有限数量的方法将采用一组样式（例如printText，在您的示例中），您可以调整它们的签名以采用可变数量的样式参数：
void printText(String text, Style... flags) {
EnumSet<Style> style = logicalOr(flags); // see comment below
...
}
And then your calls are very close to the untyped (int) flag route:
然后你的电话非常接近无类型（int）标志路线：
printText("hello", Style.BOLD, Style.ITALIC);
Sadly, there is no EnumSet.of(E... )factory, just EnumSet.of(E first, E... more), so you'll need a generic logicalOrmethod to split your array into first + rest chunks. Left as an exercise to the reader =).
遗憾的是，没有EnumSet.of(E... )工厂，只有EnumSet.of(E first, E... more)，因此您需要一个通用logicalOr方法将数组拆分为 first + rest 块。 作为练习留给读者 =)。
