Trim leading or trailing characters from a string?

Question

How can I trim the leading or trailing characters from a string in java?

For example, the slash character "/" - I'm not interested in spaces, and am looking to trim either leading or trailing characters at different times.

Answer 1

You could use

Leading:

System.out.println("//test/me".replaceAll("^/+", ""));

Trailing:

System.out.println("//test/me//".replaceAll("/+$", ""));

Answer 2

You can use Apache StringUtils.stripStart to trim leading characters, or StringUtils.stripEnd to trim trailing characters.

For example:

System.out.println(StringUtils.stripStart("//test/me", "/"));

will output:

test/me

Note that if for some reason you can't use the whole StringUtils library, you could just rip out the relevant parts, as detailed here:

Answer 3

Trim with Character, String, or Regex

_{If run-time is not a big issue for you, then this code will prove really helpful.}

public class StringTrimmer {
    public static String trim(String string, char ch){
        return trim(string, ch, ch);
    }

    public static String trim(String string, char leadingChar, char trailingChar){
        return string.replaceAll("^["+leadingChar+"]+|["+trailingChar+"]+$", "");
    }

    public static String trim(String string, String regex){
        return trim(string, regex, regex);
    }

    public static String trim(String string, String leadingRegex, String trailingRegex){
        return string.replaceAll("^("+leadingRegex+")+|("+trailingRegex+")+$", "");
    }

    // test
    public static void main(String[] args) {
        System.out.println(trim("110100", '1', '0')); // outputs: 01
        System.out.println(trim("**Aa0*#**", '*')); // outputs: Aa0*#
        System.out.println(trim("123##22222", "12", "22")); // outputs: 3##2
        System.out.println(trim("101101##10101", "101")); // outputs: ##10
        System.out.println(trim("123##abcde", "\\d", "[c-e]")); // outputs: ##ab
    }
}

Answer 4

For those using Spring:

https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/util/StringUtils.html#trimTrailingCharacter-java.lang.String-char-

import org.springframework.util.StringUtils;    

public void setFileName(String fileName) {
    // If the extension does not exist trim the trailing period
    this.fileName = StringUtils.trimTrailingCharacter(fileName,'.');
}

Answer 5

You could use a simple iteration if you want to remove the leading characters from a string :

String removeLeadingChar(String s, char c) {
    int i;
    for(i = 0; i < s.length() && s.charAt(i) == c; ++i);
    return s.substring(i);
}

same logic applies if you want to remove any trailing char.

Answer 6

My version of trimming leading and/or trailing String s from String str. Both arguments may be null. When str does not has leading and/or trailing s, it is not changed.

String trim(String str, String s) {
    String res = s == null ? str : str == null ? null : s.length() >= str.length() ? str : str.replaceFirst(s, "");
    if ((res != null) && (s != null) && (res.length() >= s.length())) {
        return res.substring(res.length() - s.length(), res.length()).equals(s) ? res.substring(0, res.length() - s.length()) : res;
    }
    return res;
}