java 在java中使用枚举有什么好处？
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what is the advantage of using enum in java?
提问by user1720500
I was going through the enums in Java. The same what an enum can do can be achieved by collections or an array of Strings or user-defined types. What is the main purpose of introducing enums in Java 5.
我正在浏览 Java 中的枚举。枚举可以做的事情可以通过集合或字符串数组或用户定义类型来实现。在 Java 5 中引入枚举的主要目的是什么？
Thanks, Sehensaa
谢谢，Sehensaa
回答by Subhrajyoti Majumder
Advantages -
好处 -
- Set of Constant declaration
- Restrict input parameter in method
- Can be usable in switch-case
- 常量声明集
- 限制方法中的输入参数
- 可用于开关盒
It is used for fields consist of a fixed set of constants.
它用于由一组固定常量组成的字段。
Example is Thread.State
例子是 Thread.State
public enum State {
NEW,
RUNNABLE,
WAITING,
BLOCKED,
...
}
or private enum Alignment { LEFT, RIGHT };
或者 private enum Alignment { LEFT, RIGHT };
You can restrict input parameter using Enumlike-
您可以使用Enum类似限制输入参数-
String drawCellValue (int maxCellLnghth, String cellVal, Alignment align){}
Here in align parameter could be only Alignment.LEFTor Alignment.RIGHTwhich is restricted.
这里的 align 参数可以是唯一的Alignment.LEFT或Alignment.RIGHT受限制的。
Example of switch-case with enum-
带有enum-的开关盒示例
String drawCellValue (int maxCellLnghth, String cellVal, Alignment align){
switch (align) {
case LEFT:...
case RIGHT: ...
}
...
}
回答by Sumit Singh
From understanding-enums-in-java
- Type safety. You can declare a function argument, return type, class member or local variable to be a particular Enum type and the compiler will enforce type safety;
- Enums are basically classes. They can implement interfaces, have behaviour and so on.
- 类型安全。您可以将函数参数、返回类型、类成员或局部变量声明为特定的 Enum 类型，编译器将强制执行类型安全；
- 枚举基本上是类。他们可以实现接口，拥有行为等等。
From enum-in-java-advantages
You get free compile time checking of valid values. Using
从enum-in-java-advantages
您可以获得有效值的免费编译时检查。使用
public static int OPTION_ONE = 0;
public static int OPTION_TWO = 1;
回答by robertboloc
one of it's uses was as a means to emulate a switchon Strings type variables as before Java 7 this was not allowed
它的用途之一是switch作为在 Java 7 之前模拟Strings 类型变量的一种方法，这是不允许的
回答by Puce
Have a look for the "type-safe enum pattern" (e.g. in the book "Effective Java" 1st edition, by Joshua Bloch). The Java "enum" construct is a language level support (syntactic sugar) for this design pattern.
看看“类型安全的枚举模式”（例如，在 Joshua Bloch 的“Effective Java”第一版一书中）。Java“枚举”构造是此设计模式的语言级别支持（语法糖）。
