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

Question

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?

Answer 1

Since JDK 11

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

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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

• Java regular expression syntax