I want to have a function that returns true, when I compare a null String and an Empty String

Question

I need to compare an empty("") String and a Null String and return true.

String a = "";
String b = null;

// return TRUE if I compare "" and null
return TRUE if I compare null and null
return TRUE if I compare "" and ""

return false if a or b has some value

This is trivially easy to do, what exactly are you stuck on? — JonK, Jun 11 '19 at 15:07
and `""` compared to `""` should not also return `true` ? Same thing for `null` and `null`. Your requirement is unclear. — davidxxx, Jun 11 '19 at 15:11
@davidxxx "" compared to "" should give true, null compared to null should give true, "" compared to null should also give true — Trishul Singh Choudhary, Jun 11 '19 at 15:12
So in the end you want both variables to be null or empty. There is no comparison necessary — wero026, Jun 11 '19 at 15:15
@Zephyr Because that would throw a `NullPointerException` if `a` or `b` was `null` — JonK, Jun 11 '19 at 15:20
@rw026 Yes, I should get true on comparing null and "" , That's my actual question. — Trishul Singh Choudhary, Jun 11 '19 at 15:44

score 1 · Answer 1 · answered Jun 11 '19 at 15:16

1

You could use a function to not repeat yourself :

String a = ...;
String b = ...;

Predicate<String> isNullOrEmpty = s -> s == null || s.equals("");
return isNullOrEmpty.test(a) && isNullOrEmpty.test(b);

You can also rely on Apache Command Lang that provides StringUtils.isEmpty() :

return StringUtils.isEmpty(a) && StringUtils.isEmpty(b);

answered Jun 11 '19 at 15:16

davidxxx

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What if a or b has some value ? – Trishul Singh Choudhary Jun 11 '19 at 15:51
It returns false. You could write an unit test and you could check all of that – davidxxx Jun 11 '19 at 15:57

wero026 · Answer 2 · 2019-06-12T08:04:10.527

0

Your actual usecase is not to compare the strings to each other but instead you want to check if one of both is not empty.

The following snippet should do the job:

public boolean func(String a, String b) {
    if (a != null && !a.isEmpty()) {
        return false;
    }
    if (b != null && !b.isEmpty()) {
        return false;
    }
    return true;
}

edited Jun 12 '19 at 08:04

answered Jun 11 '19 at 15:19

wero026

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I want to have a function that returns true, when I compare a null String and an Empty String

2 Answers2