Java how to replace 2 or more spaces with single space in string and delete leading and trailing spaces

by

Try this:

String after = before.trim().replaceAll(" +", " ");

See also

No trim() regex

It’s also possible to do this with just one replaceAll, but this is much less readable than the trim() solution. Nonetheless, it’s provided here just to show what regex can do:

    String[] tests = {
        "  x  ",          // [x]
        "  1   2   3  ",  // [1 2 3]
        "",               // []
        "   ",            // []
    };
    for (String test : tests) {
        System.out.format("[%s]%n",
            test.replaceAll("^ +| +$|( )+", "$1")
        );
    }

There are 3 alternates:

  • ^_+ : any sequence of spaces at the beginning of the string
    • Match and replace with $1, which captures the empty string
  • _+$ : any sequence of spaces at the end of the string
    • Match and replace with $1, which captures the empty string
  • (_)+ : any sequence of spaces that matches none of the above, meaning it’s in the middle
    • Match and replace with $1, which captures a single space

See also

More Related Contents:

  1. How can non-ASCII characters be removed from a string?
  2. Replace the last part of a string
  3. Java String.replace/replaceAll not working
  4. String.replaceAll is considerably slower than doing the job yourself
  5. Remove all occurrences of \ from string
  6. Regex for converting xml tags key to camel case
  7. How to split a string if any chracter is found in java
  8. Java: splitting a comma-separated string but ignoring commas in quotes
  9. Splitting a Java String by the pipe symbol using split(“|”)
  10. Split string to equal length substrings in Java
  11. Split string with dot as delimiter
  12. Why does String.split need pipe delimiter to be escaped?
  13. Strip Leading and Trailing Spaces From Java String
  14. Using Java to find substring of a bigger string using Regular Expression
  15. How to replace case-insensitive literal substrings in Java
  16. How to use regex in String.contains() method in Java
  17. Compare one String with multiple values in one expression
  18. How do I convert CamelCase into human-readable names in Java?
  19. Remove trailing zero in Java
  20. Extract string between two strings in java
  21. What is the simplest way to convert a Java string from all caps (words separated by underscores) to CamelCase (no word separators)?
  22. Java String.split() Regex
  23. Check if string ends with certain pattern
  24. Remove all non-“word characters” from a String in Java, leaving accented characters?
  25. How to implement a SQL like ‘LIKE’ operator in java?
  26. What is the equivalent of Regex-replace-with-function-evaluation in Java 7?
  27. Raw Strings in Java – for regex in particular. Multiline strings
  28. Replace Last Occurrence of a character in a string [duplicate]
  29. Replacing single ‘\’ with ‘\\’ in Java
  30. Hints for java.lang.String.replace problem? [duplicate]

Leave a Comment