哈希映射键的空检查 [英] null check for hashmap key
问题描述
我有一个需要检查 null
的场景.我有一个名为 dT
的密钥:
String dT = (String) caseChk.get("dT");
这会抛出一个 NullPointerException
,因为该键本身不存在.如果我检查
if(caseChk.get("dT") != null) {//做一点事}
又一个 NullPointerException
由于 .get
被抛出.当映射中的键不存在时,如何测试 null
?我知道 put
方法应该处理它,但这不在我的控制之下.]
即使现在我得到 nullpoiner 因为 .get 抛出异常
如果 caseChk.get("dT")
只是你在那里的行并且确定它正在抛出异常,那么唯一的可能性是 caseChk
可能为空.>
I have a scenario where I need to check for null
. I have a key named dT
:
String dT = (String) caseChk.get("dT");
This throws a NullPointerException
, since that key itself doesn't exist. If I check with
if(caseChk.get("dT") != null) {
// do something
}
yet another NullPointerException
is thrown because of .get
. How can I test for null
when a key in the map doesn't exist? I understand that the put
method should handle it, but that isn't under my control.]
Even now I get nullpoiner since .get throws exception
If caseChk.get("dT")
is only line you have there and sure it is throwing exception, then only possibility is caseChk
could be null.
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