What is a good alternative of LTRIM and RTRIM in Java?

Solution 1:

With a regex you could write:

String s = ...
String ltrim = s.replaceAll("^\\s+","");
String rtrim = s.replaceAll("\\s+$","");

If you have to do it often, you can create and compile a pattern for better performance:

private final static Pattern LTRIM = Pattern.compile("^\\s+");

public static String ltrim(String s) {
    return LTRIM.matcher(s).replaceAll("");
}

From a performance perspective, a quick micro benchmark shows (post JIT compilation) that the regex approach is about 5 times slower than the loop (0.49s vs. 0.11s for 1 million ltrim).

I personally find the regex approach more readable and less error prone but if performance is an issue you should use the loop solution.

Solution 2:

Using regex may be nice, but it's quite a lot slower than a simple trimming functions:

public static String ltrim(String s) {
    int i = 0;
    while (i < s.length() && Character.isWhitespace(s.charAt(i))) {
        i++;
    }
    return s.substring(i);
}

public static String rtrim(String s) {
    int i = s.length()-1;
    while (i >= 0 && Character.isWhitespace(s.charAt(i))) {
        i--;
    }
    return s.substring(0,i+1);
}

Source: http://www.fromdev.com/2009/07/playing-with-java-string-trim-basics.html

Also, there are some libraries providing such functions. For example, Spring StringUtils. Apache Commons StringUtils provides similar functions too: strip, stripStart, stripEnd

StringUtils.stripEnd("abc  ", null)    = "abc"

Solution 3:

import org.apache.commons.lang3.StringUtils;

private String rTrim(String str) {
    return StringUtils.stripEnd(str, /*stripChars*/" ");
}

private String lTrim(String str) {
    return StringUtils.stripStart(str, /*stripChars*/" ");
}

Solution 4:

You can simply try the following

String s = "  Hello world  "

String ltrim = s.stripLeading();

String rtrim = s.stripTrailing();

Solution 5:

Guava has CharMatcher trimLeadingFrom and trimTrailingFrom

e.g. CharMatcher.whitespace.trimTrailingFrom(s)