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Java Forum / General / August 2006how compare two string?
Hello, I must find a method that verification if two strings are equal or not. The text comes extracted from a file and there are some empty lines. I have tried with the method equals(), and also compareTo() of the class String, but they return java.lang.NullPointerException when they find the line empty. How I make to arrive at the end of the rows? Thanks P.S. Sorry for my English Elbrethril schreef: > Hello, I must find a method that verification if two strings are equal > or not. The text comes extracted from a file and there are some empty > lines. I have tried with the method equals(), and also compareTo() of > the class String, but they return java.lang.NullPointerException when > they find the line empty. How I make to arrive at the end of the rows? equals() is the right method, but you’ll have to do a not-null check first, to see whether the object you’re invoking it on is not null. However, I would expect empty lines to return "", not null. Can you post some code? Also look for the idiom "some string".equals(varString); H. - -- Hendrik Maryns ================== http://aouw.org Ask smart questions, get good answers: http://www.catb.org/~esr/faqs/smart-questions.html > equals() is the right method, but you'll have to do a not-null check > first, to see whether the object you're invoking it on is not null. > However, I would expect empty lines to return "", not null. Can you > post some code? > > Also look for the idiom "some string".equals(varString); ok, but the object is not null, because until it does not find the null line returns the right string. String line = ""; BufferedReader in = null; in = new BufferedReader(new FileReader("DatasetPiccolo.txt")); String key = null; while (line != null) String readed = getTag(line); if (readed == "authors") { key = getValue(line); System.out.println(authors); } getTag is a method for delete some characters from the string. getValue is for extract the text that I want. Elbrethril schreef: >> equals() is the right method, but you'll have to do a not-null check >> first, to see whether the object you're invoking it on is not null. [quoted text clipped - 14 lines] > > if (readed == "authors") "authors".equals(readed) > { > key = getValue(line); > System.out.println(authors); > } as I suggested. H. P.S. ‘readed’ is very odd English. It is ‘read’, pronounced like the colour. - -- Hendrik Maryns ================== http://aouw.org Ask smart questions, get good answers: http://www.catb.org/~esr/faqs/smart-questions.html Hendrik Maryns ha scritto: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 [quoted text clipped - 32 lines] > - -- > Hendrik Maryns thanks! I didn't realize 'read' was a colour ;-) --Norman > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 [quoted text clipped - 44 lines] > =f5BK > -----END PGP SIGNATURE----- > I didn't realize 'read' was a colour ;-) Certainly it is... Q: What's black and white and read all over? A: A newspaper. Luke I stand corrected! --Norman > > I didn't realize 'read' was a colour ;-) > [quoted text clipped - 5 lines] > > Luke > ok, but the object is not null, because until it does not find the null > line returns the right string. [quoted text clipped - 14 lines] > getTag is a method for delete some characters from the string. getValue > is for extract the text that I want. In addition to the String comparison issue, the posted example fails to actually read from the file, so you will never find what you are looking for. In order to read the file one like at a time, the loop should look like this: while ((line = in.readLine()) != null) { // process line ... } /gordon  Signature[ don't email me support questions or followups ] g o r d o n + n e w s @ b a l d e r 1 3 . s e >> equals() is the right method, but you'll have to do a not-null check >> first, to see whether the object you're invoking it on is not null. [quoted text clipped - 12 lines] > while (line != null) > String readed = getTag(line); The program will loop forever at this point, because line will never be null. [rest of program snipped] - Oliver Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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