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javaandroidstringtrim

How to remove only trailing spaces of a string in Java and keep leading spaces?

The trim() function removes both the trailing and leading space, however, if I only want to remove the trailing space of a string, how can I do it?

Solution

  • Since JDK 11

    If you are on JDK 11 or higher you should probably be using stripTrailing().

    Earlier JDK versions

    Using the regular expression \s++$, you can replace all trailing space characters (includes space and tab characters) with the empty string ("").

    final String text = "  foo   ";
System.out.println(text.replaceFirst("\\s++$", ""));

    Output

      foo

    Online demo.

    Here's a breakdown of the regex:

    • \s – any whitespace character,
    • ++ – match one or more of the previous token (possessively); i.e., match one or more whitespace character. The + pattern is used in its possessive form ++, which takes less time to detect the case when the pattern does not match.
    • $ – the end of the string.

    Thus, the regular expression will match as much whitespace as it can that is followed directly by the end of the string: in other words, the trailing whitespace.

    The investment into learning regular expressions will become more valuable, if you need to extend your requirements later on.

    References