在 Java 枚举上实现 toString
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Implementing toString on Java enums
提问by devoured elysium
It seems to be possible in Java to write something like this:
在 Java 中似乎可以编写如下内容：
private enum TrafficLight {
RED,
GREEN;
public String toString() {
return //what should I return here if I want to return
//"abc" when red and "def" when green?
}
}
Now, I'd like to know if it possible to returnin the toString method "abc" when the enum's value is red and "def" when it's green. Also, is it possible to do like in C#, where you can do this?:
现在，我想知道是否可以在枚举值为红色时返回 toString 方法“abc”和绿色时返回“def”。另外，是否可以像在 C# 中那样做，您可以在哪里执行此操作？：
private enum TrafficLight {
RED = 0,
GREEN = 15
...
}
I've tried this but it but I'm getting compiler errors with it.
我试过这个，但它但我收到编译器错误。
Thanks
谢谢
采纳答案by missingfaktor
Ans 1:
答案 1：
enum TrafficLight {
RED,
GREEN;
@Override
public String toString() {
switch(this) {
case RED: return "abc";
case GREEN: return "def";
default: throw new IllegalArgumentException();
}
}
}
Ans 2:
答案 2：
enum TrafficLight {
RED(0),
GREEN(15);
int value;
TrafficLight(int value) { this.value = value; }
}
回答by jjnguy
You can do it as follows:
你可以这样做：
private enum TrafficLight {
// using the constructor defined below
RED("abc"),
GREEN("def");
// Member to hold the name
private String string;
// constructor to set the string
TrafficLight(String name){string = name;}
// the toString just returns the given name
@Override
public String toString() {
return string;
}
}
You can add as many methods and members as you like. I believe you can even add multiple constructors. All constructors must be private.
您可以根据需要添加任意数量的方法和成员。我相信您甚至可以添加多个构造函数。所有构造函数都必须是private.
An enumin Java is basically a classthat has a set number of instances.
enumJava 中的an基本上是class具有一组实例的 a 。
回答by user3054516
Also if You need to get lowercase string value of enum ("red", "green") You can do it as follows:
此外，如果您需要获取枚举的小写字符串值（“红色”，“绿色”），您可以按如下方式进行：
private enum TrafficLight {
RED,
GREEN;
@Override
public String toString() {
return super.toString().toLowerCase();
}
}
