Value comparison is confusing me, not working properly

Question

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I am comparing two strings, and apparently they aren't equal but they are. I was wondering what are some issues that could cause this, maybe datatype, hidden stuff that I can't see, or what. Any input could be helpful. Thanks.

You're **not** doing value comparison; the `==` operator when applied to objects does *reference* comparison - it will only return true if they're the exact same object. — Anthony Grist, Jan 17 '13 at 16:10

score 2 · Accepted Answer · edited May 23 '17 at 12:12

2

String/Object comparison should use equals(), not == (excepts the case of String literal comparison)

Example:

if(string.equals(string2)){
}

== checks for reference equality, equals() checks for content equality. Read this discussion.

edited May 23 '17 at 12:12

Community

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answered Jan 17 '13 at 16:09

kosa

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Just to add to this: == checks whether the references to the objects are equal, .equals() checks for character sequence equality – Justin Jasmann Jan 17 '13 at 16:11
Thanks everyone. Is this true for C++ too or Java specific? – Jackson Bray Jan 17 '13 at 16:15
@user1582340: Don't know about C++, but it is true in Java, not true in .NET – kosa Jan 17 '13 at 16:16
Personally, I'd avoid using `==` even when comparing String literals in Java, in case one of them _stops_ being a literal. – Clockwork-Muse Jan 17 '13 at 16:34

Achintya Jha · Answer 2 · 2013-01-17T16:29:22.733

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field.trim().equalsIgnoreCase("formDateCreated")

Try this. String trim() Method returns a copy of the string, with leading and trailing whitespace omitted.

edited Jan 17 '13 at 16:29

answered Jan 17 '13 at 16:19

Achintya Jha

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"formDateCreated".trim() no need to trim here since no spaces here – someone Jan 17 '13 at 16:24
Yes,I know but may be user1582340 getting problem because of this. – Achintya Jha Jan 17 '13 at 16:27
No trim is note the issue. But you don't need to trim() this "formDateCreated" – someone Jan 17 '13 at 16:28

score 1 · Answer 3 · edited Jan 17 '13 at 16:27

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use .equals() method to check for String equality like field1.equals("formDateCreated"). == operator just checks if two reference variables refer to the same string instance. equals() method checks if two strings are meaningfully equal.

edited Jan 17 '13 at 16:27

someone

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answered Jan 17 '13 at 16:09

PermGenError

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someone · Answer 4 · 2013-01-17T16:22:21.283

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equalsIgnoreCase(String anotherString)

for when you are not consider about case. This check weather your string content is equal not the reference which is ==

I would suggest you to check like bellow

"formDateCreated".equalsIgnoreCase(field)

So that it helps you to overcome possible NullPointerException

edited Jan 17 '13 at 16:22

answered Jan 17 '13 at 16:10

someone

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Value comparison is confusing me, not working properly

4 Answers4