Why my strings not equal?

Question

I have 2 Strings with name str1 that fills by data from url and str2 that fills by data from SQLite Database.str1 is "x4" and str2 is "x4" but when i want to compare them,they are not equals.

if(str1.equals(str2)) System.out.println(str1 + "=" + str2);
else System.out.println(str1 + "!=" + str2);

and always it prints x4!=x4.

I changed values but always is not equals.

Try printing `System.out.println(">"+str1 + "!=" + str2+"<");` to see better . — Arnaud, Oct 11 '16 at 08:48
@Berger `System.out.println(Arrays.toString(str1.toCharArray()) + "!=" + Arrays.toString(str2.toCharArray()));` would help you see a lot better. — Andy Turner, Oct 11 '16 at 08:49
no because i did str1 = "a" + str1 + "a" and str2 = "a" + str2 + "a" and they have no trailing spaces — Esmail Jamshidiasl, Oct 11 '16 at 08:50
Could it be encoding issue? Try testing in if: new String(str1, UTF_8).equals(new String(str2, UTF_8)) — Arne H. Bitubekk, Oct 11 '16 at 08:53
@ArneHB It can't possibly be encoding and the constructor you suggest doesn't even exist. — Marko Topolnik, Oct 11 '16 at 09:02
@MarkoTopolnik Sorry you are right, it takes a byte array and not string as parameter so you'll have to do it like this: byte bStr1[] = str1.getBytes(ISO_8859_1); new String(bStr1, UTF_8); http://docs.oracle.com/javase/7/docs/api/java/lang/String.html — Arne H. Bitubekk, Oct 11 '16 at 10:50
@ArneHB OP already has two strings that `println` renders equally. Encoding has nothing to do with this problem. — Marko Topolnik, Oct 11 '16 at 10:51

score 2 · Answer 1 · answered Oct 11 '16 at 08:48

Database.str1 is "x4" and str2 is "x4"

It might look like that, but I bet that's not the case. Why not print out the char array for each string, and that way you can identify what differs? I would suggest looking for leading/trailing spaces, non-printing characters, Unicode-related differences etc.

score 1 · Accepted Answer · answered Oct 11 '16 at 09:03

Try changing it to:

StringBuilder string = new StringBuilder();
string.append("'");
string.append(str1);
string.append("'");

if(!str1.equals(str2)){
    string.append("!");
}

string.append("'");
string.append(str2);
string.append("'");
System.out.println(string.toString());

It is most likely that there is a space, enter or a tab in one of the strings. By adding a character at the start and end of each string then you can identify if that is the case.

If the problem persists then that probably means that one of the characters that is different is not printable. In that case try:

string.append(str1.toCharArray());

instead of

string.append(str1);

And do the same for str2.

score 0 · Answer 3 · edited May 23 '17 at 12:02

0

It could have been caused either due to trailing spaces, as a_horse_with_no_name said, or (maybe you didn't notice) due to case difference. Try this:

if(str1.trim().equalsIgnoreCase(str2.trim()))
    System.out.print(str1 + "=" + str2);
else
    System.out.print(str1 + "!=" + str2);

Use trim() to remove trailing spaces and use equalsIgnoreCase() instead of equals(), considering case difference.

edited May 23 '17 at 12:02

Community

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answered Oct 11 '16 at 09:06

progyammer

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I'm not sure that is what OP asked. He asked why they are not equal, not what he should do so that they pass the statement. But if I'm wrong then your is correct. – nick zoum Oct 11 '16 at 09:08
What if the difference isn't at the end of the strings? e.g. `Ab` and `A\0b` look the same in my console, but the `\0` won't be removed. – Andy Turner Oct 11 '16 at 09:18
@AndyTurner In that case, wouldn't the strings just be "unequal"? – progyammer Oct 11 '16 at 09:48
1

Indeed. But OP is asking why two strings which "look equal" aren't. – Andy Turner Oct 11 '16 at 09:48

Why my strings not equal?

3 Answers3