Java 带字符串的 switch 语句中的常量表达式需要错误
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Constant expression required error in switch statement with strings
提问by Isuru
I get a JSON response which roughly looks like this.
我得到一个大致如下所示的 JSON 响应。
{
"status": "success",
"data": [
{
....
}
]
}
The statusfield can have two values: successor fail.
该status字段可以有两个值：success或fail。
So in my code, I have the following enum.
所以在我的代码中，我有以下枚举。
private enum Status {
SUCCESS("success", 0),
FAIL("fail", 1);
private String stringValue;
private int intValue;
private Status(String toString, int value) {
stringValue = toString;
intValue = value;
}
@Override
public String toString() {
return stringValue;
}
}
What I want to do is in a switch statement, I need to check for the status value and execute code in each condition.
我想要做的是在 switch 语句中，我需要检查状态值并在每个条件下执行代码。
String status = jsonObj.getString("status");
switch (status) {
case Status.SUCCESS.toString():
Log.d(LOG_TAG, "Response is successful!");
case Status.FAIL.toString():
Log.d(LOG_TAG, "Response failed :(");
default:
return;
}
But I get the Constant expression requirederror at each case.
但是我在每种情况下都会得到Constant expression required错误。
I checked the value returned by Status.SUCCESS.toString()and Status.FAIL.toString()which indeed return strings.
我检查了返回的值，Status.SUCCESS.toString()并且Status.FAIL.toString()确实返回了字符串。
Any idea why this error still occur?
知道为什么这个错误仍然发生吗？
采纳答案by Bathsheba
casestatements have to be compile-time evaluable.
case语句必须是编译时可评估的。
Something like Status.SUCCESS.toString()doesn't satisfy that. A string literal, on the other hand, does.
类似的东西Status.SUCCESS.toString()不能满足这一点。另一方面，字符串文字可以。
The obvious fix is to use an an ifblock.
显而易见的解决方法是使用一个if块。
