String.ValueOf() to replace NULL with string null when calling a method

Question

I'm trying to use String.valueOf() to replace the null when i'm calling some method.But it still shows nullpointerexception. This may be simple but i'm missing something.

I have statement like this

myvar = this.kind.name().toLowerCase()

It is throwing java.lang.NullPointerException. Im trying to keep string "NULL" whenever i get NPE. so i tried this

myvar = String.valueOf(this.kind.name().toLowerCase()) -- not working

I have found from other posts that it may not work as we have overloaded method String.valueOf(char[]) and String.valueOf(object) and suggested to use below. But still it s not working. How do i assign string null in this case?

myvar = String.valueOf((this.kind.name().toLowerCase()) null))

@joe , I'm not asking what is `nullpointerexception`. Please read the question. — Arun Palanisamy, Apr 02 '19 at 11:05
Show the NPE trace. I expect name() (which should be getName()?) to return NULL. — ChristophS, Apr 02 '19 at 11:05
@Crazy2crack If `this.kind` is null, you should be able to determine that from the stacktrace. You can handle the situation by adding an if-condition or code like `String.valueOf(this.kind == null ? null : this.kind.name()).toLowercase()`. — rsp, Apr 02 '19 at 11:22
@rsp. Yes `this.kind` is null. It worked. Can you please post this as answer. I will mark it as correct. — Arun Palanisamy, Apr 02 '19 at 11:24

score 10 · Answer 1 · answered Apr 02 '19 at 11:06

10

You should be using

myvar = String.valueOf(this.kind.name()).toLowerCase();

not

myvar = String.valueOf(this.kind.name().toLowerCase());

As documentation of valueOf() describes

if the argument is null, then a string equal to "null"; otherwise, the value of obj.toString() is returned

So,String.valueOf(this.kind.name()) would return "null"

answered Apr 02 '19 at 11:06

Ashishkumar Singh

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Thanks but unfortunately, it is still throwing the NPE :( – Arun Palanisamy Apr 02 '19 at 11:12
Debug your code and check what does `String.valueOf(this.kind.name())` returns – Ashishkumar Singh Apr 02 '19 at 11:12
@Crazy2crack: So add stack trace to see, who's throwing the exception – ChristophS Apr 02 '19 at 11:12

score 4 · Accepted Answer · answered Apr 02 '19 at 11:28

4

If this.kind is null, you should be able to determine that from the stacktrace.

You can handle the situation by adding an if-condition or code like

String.valueOf(this.kind == null ? null : this.kind.name()).toLowercase()

answered Apr 02 '19 at 11:28

rsp

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String.ValueOf() to replace NULL with string null when calling a method

2 Answers2