How to remove line breaks from a file in Java

Question

How can I replace all line breaks from a string in Java in such a way that will work on Windows and Linux  ie no OS specific problems of carriage return line feed new line etc     I ve tried  note readFileAsString is a function that reads a text file into a String              String text   readFileAsString  textfile txt    text replace   n          but this doesn t seem to work   How can this be done

User · Answer

As noted in other answers  your code is not working primarily because String replace      does not change the target String    It can t - Java strings are immutable    What replace actually does is to create and return  a new String object with the characters changed as required   But your code then throws away that String      Here are some possible solutions   Which one is most correct depends on what exactly you are trying to do      1 text   text replace  quot  n quot    quot  quot     Simply removes all the newline characters   This does not cope with Windows or Mac line terminations      2 text   text replace System getProperty  quot line separator quot     quot  quot     Removes all line terminators for the current platform   This does not cope with the case where you are trying to process  for example  a UNIX file on Windows  or vice versa      3 text   text replaceAll  quot   r   n quot    quot  quot     Removes all Windows  UNIX or Mac line terminators   However  if the input file is text  this will concatenate words  e g  Goodbye cruel world   becomes Goodbye cruelworld   So you might actually want to do this      4 text   text replaceAll  quot   r  n   r   n quot    quot   quot     which replaces each line terminator with a space1   Since Java 8 you can also do this      5 text   text replaceAll  quot   R quot    quot   quot     And if you want to replace multiple line terminator with one space      6 text   text replaceAll  quot   R  quot    quot   quot      1 - Note there is a subtle difference between  3 and  4   The sequence  r n represents a single  Windows  line terminator  so we need to be careful not to replace it with two spaces

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String text   readFileAsString  textfile txt   replaceAll   n          Even though the definition of trim   in oracle website is   Returns a copy of the string  with leading and trailing whitespace omitted    the documentation omits to say that new line characters  leading and trailing  will also be removed   In short String text   readFileAsString  textfile txt   trim    will also work for you    Checked with Java 6

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Try doing this    textValue  textValue replaceAll   n         textValue  textValue replaceAll   t         textValue  textValue replaceAll    n         textValue  textValue replaceAll    t         textValue  textValue replaceAll   r         textValue  textValue replaceAll    r         textValue  textValue replaceAll   r n         textValue  textValue replaceAll    r  n

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org apache commons lang StringUtils chopNewline

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You may want to read your file with a BufferedReader  This class can break input into individual lines  which you can assemble at will  The way BufferedReader operates recognizes line ending conventions of the Linux  Windows and MacOS worlds automatically  regardless of the current platform   Hence   BufferedReader br   new BufferedReader      new InputStreamReader  textfile txt     StringBuilder sb   new StringBuilder    for            String line   br readLine        if  line    null          break      sb append line       sb append            SEE BELOW   String text   sb toString      Note that readLine   does not include the line terminator in the returned string  The code above appends a space to avoid gluing together the last word of a line and the first word of the next line

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FYI if you can want to replace simultaneous muti-linebreaks with single line break then you can use  myString trim   replaceAll    n  2       n     Or replace with a single space  myString trim   replaceAll    n  2

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Linebreaks are not the same under windows linux mac  You should use System getProperties with the attribute line separator

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This function normalizes down all whitespace  including line breaks  to single spaces   Not exactly what the original question asked for  but likely to do exactly what is needed in many cases   import org apache commons lang3 StringUtils   final String cleansedString   StringUtils normalizeSpace rawString

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You can use apache commons IOUtils to iterate through the line and append each line to StringBuilder  And don t forget to close the InputStream   StringBuilder sb   new StringBuilder    FileInputStream fin new FileInputStream  textfile txt    LineIterator lt IOUtils lineIterator fin   utf-8    while lt hasNext        sb append lt nextLine       String text   sb toString    IOUtils closeQuitely fin

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I find it odd that  Apache  StringUtils wasn t covered here yet   you can remove all newlines  or any other occurences of a substring for that matter  from a string using the  replace method  StringUtils replace myString    n          This line will replace all newlines with the empty string    because newline is technically a character you can optionally use the  replaceChars method that will replace characters  StringUtils replaceChars myString    n

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str   str replaceAll    r  n   r   n           Worked perfectly for me after searching a lot  having failed with every other line

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String text   readFileAsString  textfile txt   replace   n          replace returns a new string  strings in Java are Immutable

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If you want to remove only line terminators that are valid on the current OS  you could do this   text   text replaceAll System getProperty  line separator           If you want to make sure you remove any line separators  you can do it like this   text   text replaceAll    r   n          Or  slightly more verbose  but less regexy   text   text replaceAll    r       replaceAll    n

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You can use generic methods to replace any char with any char   public static void removeWithAnyChar String str  char replceChar          char replaceWith        char chrs     str toCharArray        int i   0      while  i  lt  chrs length             if  chrs i     replceChar                chrs i    replaceWith                    i

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This would be efficient I guess  String s  s    try this n try me    s replaceAll     r  n

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You need to set text to the results of text replace     String text   readFileAsString  textfile txt    text   text replace   n       replace   r          This is necessary because Strings are immutable -- calling replace doesn t change the original String  it returns a new one that s been changed   If you don t assign the result to text  then that new String is lost and garbage collected   As for getting the newline String for any environment -- that is available by calling System getProperty  line separator

[java] How to remove line breaks from a file in Java?

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