Member Avatar for Fenerbahce

hi,

i receive an error on this line -- if (salesPersonsName <! "end") --

error : operator ! cannot be applied to java.lang.String

what can i do?

thanks

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  • Latest Post Latest Post by masijade

Dani AI

Generated

Short answer: the unary ! operator only works on boolean values, not on String objects — is correct. The original <! looks like a mistyped attempt to express “not equal” or “not 'end'”. For string content checks you need a boolean expression that compares the string contents, and then you can negate that boolean.

Practical, null-safe patterns to avoid the common NullPointerException: prefer comparing a constant to the variable or use java.util.Objects. For example, build a trimmed, non-null value first and then test it; or use Objects.equals for a null-tolerant equality test. These approaches avoid the common bug where the input is null or has stray whitespace.

If you want case-insensitive sentinel handling use a case-insensitive comparison; if you actually need ordering (alphabetical greater/less), use a lexicographic comparison and check the returned integer as suggested. Avoid using == to test string content — that checks reference identity, not content, and will often give the wrong result.

Quick checklist:

  • Did you mean “not equal”? use a string equality boolean and negate that (null-safe).
  • Did you mean “alphabetical order”? use the lexicographic compare and test <0, =0, >0.
  • Trim input and consider equalsIgnoreCase for user-typed sentinels like "end".
  • Prefer Objects.equals(a, b) or "end".equals(variable)-style constant-first checks to prevent NPEs.
  • If reading repeatedly from input, normalize (trim + toLowerCase) once and reuse that normalized value for comparisons.

References in thread: (OP), (note about booleans), (pointing toward equals), and (ordering via compare).

Recommended Answers

All 6 Replies

Member Avatar for jwenting

you can't negate a String, only a boolean.
I've no clue what you're trying to accomplish there so can't help you out.

Member Avatar for masijade

Are you trying to say "not less than", if so why don't you just say "greater than"?

>
// instead of
<!

Edit: Nevermind, I'm an idiot, they're Strings so greater than and less than are not what you want anyway. Doh!

Member Avatar for eniacad

if you want to compare strings use compareTo() method ex: oneString.compareTo(anotherString). if oneString is greater then anotherString the method will return value >0, it it is less --> value <0, and if they are equal -->value =0.

I hope that this will help you.

Cao

Member Avatar for masijade

I knid of doubt that will help though, as the majority of peoples names (as the variable implies that that that is) will not be alphabetically less than end. What the OP probably wants is if (!salesPersonsName.equals("end")) . And this thread is bit old, anyway. I doubt the OP is still looking for a solution.

Member Avatar for peter_budo

I knid of doubt that will help though, as the majority of peoples names (as the variable implies that that that is) will not be alphabetically less than end. What the OP probably wants is if (!salesPersonsName.equals("end")) . And this thread is bit old, anyway. I doubt the OP is still looking for a solution.

I guess I'm missing something here. Unusual for you to reply an old thread. Did somebody posted something? Did any moderator moved anything?

Member Avatar for masijade

Someone must have moved something, or something, as this popped up in my mail as if it had been replied to, and now that I look at the post above mine, I realise that that post is old too, I had just assumed it was just posted. ;-) Ah well, sheet happens.

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