Member Avatar for cakka

Hello,

is there any other method to compare string in java beside using equal() and == operator ?

Thank you

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  • Latest Post Latest Post by stultuske

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A concise, practical follow‑up to the thread (thanks to , and ): beyond the basic reference/value debate, here are other, less obvious ways to compare strings and the real‑world gotchas to watch for.

Keep comparisons null‑safe and canonical

  • Use Objects.equals(a, b) (Java 7+) or the literal‑first pattern ("lit".equals(var)) to avoid NPEs.
  • Normalize whitespace and Unicode before comparing: use s.strip()/trim() and java.text.Normalizer to turn composed/decomposed forms into the same canonical form.
import java.util.Objects;
import java.text.Normalizer;

// null-safe
if (Objects.equals(a, b)) { /* equal */ }

// unicode-normalize
String n1 = Normalizer.normalize(s1, Normalizer.Form.NFC);
String n2 = Normalizer.normalize(s2, Normalizer.Form.NFC);
if (n1.equals(n2)) { /* equal */ }

Locale, accents and special comparisons

  • For user-facing, language‑sensitive comparison use java.text.Collator (you can ignore accents/case with setStrength).
  • For case mapping that’s predictable across locales use toLowerCase(Locale.ROOT) / toUpperCase(Locale.ROOT) (avoids Turkish ‘i’ problems).
  • Use regionMatches for case‑insensitive substring checks, contentEquals to compare a String with a CharSequence, and matches, startsWith, endsWith for pattern/prefix/suffix checks. For numeric text, parse (e.g., Integer.parseInt, BigInteger) and compare numbers instead of the raw strings.
Collator coll = Collator.getInstance(Locale.FRANCE);
coll.setStrength(Collator.PRIMARY); // ignore accents & case
if (coll.compare(s1, s2) == 0) { /* equal for user locale */ }

if (s1.regionMatches(true, 0, s2, 0, 3)) { /* first 3 chars equal, ignore case */ }

Quick decision guide

  • Nulls possible → Objects.equals or literal‑first equals.
  • User/display text → Normalizer + Collator.
  • Numeric strings → parse and compare numerically.
  • Substrings/prefixes → regionMatches / startsWith.

These cover the common pitfalls that cause surprising results even after the basics mentioned earlier.

Recommended Answers

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Member Avatar for cwarn23

It is also possible to use strvariable.equalsIgnoreCase(input) and it will compare the two strings while ignoring the difference between upper case and lower case letters. So in this method A==a and B==b etc. But besides that there isn't any other method that I am aware of.

Member Avatar for stultuske

what are you trying to compare? the reference or the value?
why would you need another way?

anyway, the 'compareTo' methods 'll work just as well.

cwarn: be careful how you explain what you say:
A==a => in light of Java this is false.

Member Avatar for cakka


thank you for your explanation


I am learning java, and I am confuse in some exercises that need a comparison

is compareTo will give a true for this : 5 == 05 ?

thank you

Member Avatar for JamesCherrill

5 and 05 are ints, not objects, so yo ucan't use compareTo directly for those values, but:
5 == 05 is true (same numeric value)
"5" == "05" is false (different tsrings)

Member Avatar for stultuske

JamesCherrill: actually, an int would change the "05" to 5.

Cakka: 5 == 05
compareTo won't give any result for that, since you are not using the method. it also depends on whether we are talking about the String class or a class you wrote yourself with it's own implementation of compareTo.

anyway, compareTo will never return true. it will return an int.

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