对 hashmap 键进行空检查

null check for hashmap key(对 hashmap 键进行空检查)

问题描述

我有一个需要检查 null 的场景.我有一个名为 dT 的键:

I have a scenario where I need to check for null. I have a key named dT:

String dT = (String) caseChk.get("dT");

这会引发 NullPointerException，因为该键本身不存在.如果我检查

This throws a NullPointerException, since that key itself doesn't exist. If I check with

if(caseChk.get("dT") != null) {
    // do something
}

又一个 NullPointerException 因为 .get 而被抛出.当地图中的键不存在时，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.]

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.]

推荐答案

即使现在我也得到了空指针，因为 .get 抛出异常

Even now I get nullpoiner since .get throws exception

如果 caseChk.get("dT") 是您那里唯一的行并且确定它正在引发异常，那么唯一的可能性是 caseChk 可能为空.

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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