CODEWITHSUNDEEP
javastringreplacestringbuilder
learner
learner

Reputation: 4818

Equivalent of rtrim with StringBuilder in java

I am trying to trim StringBuilder from right side, something like this :

private StringBuilder rtrim(StringBuilder str, Character trimStr) {
    if (str.charAt(str.length() - 1) == trimStr) {
        return str.deleteCharAt(str.length() - 1);
    }
    return str;
}

The above function works fine with character as trimStr, but I want to pass trimStr as string. Any library for the same(similar to StringUtils)?

Upvotes: 1

Views: 374

Answers (3)

Youcef LAIDANI
Youcef LAIDANI

Reputation: 60036

You can use replaceAll or just replaceFirst with regex like so :

String str = "  some string  ";
str = str.replaceAll("\\s*$", "");//output is "  some string"

Edit

If you are using StringBuilder you can use :

private static StringBuilder rtrim(StringBuilder str, String trimStr) {
    return new StringBuilder(
            str.toString().replaceFirst("(" + Pattern.quote(trimStr) + ")+$", "")
    );
}

Some inputs and outputs 

"  some string   "    + " "    ==> "  some string"
"  some stringaaa"    + "a"    ==> "  some string"
"  some stringabab"   + "ab"   ==> "  some string"

left trim (lTrim)

For left trim you can just change your regex to be str.toString().replaceFirst("^(" + Pattern.quote(trimStr) + ")+", "")

private static StringBuilder rtrim(StringBuilder str, String trimStr) {
    return new StringBuilder(
            str.toString().replaceFirst("^(" + Pattern.quote(trimStr) + ")+", "")
    );
}

Another Solution without regex

right trim (rTrim)

public StringBuilder rTrim(StringBuilder str, String trimStr) {
    if (str != null && trimStr != null) {
        int trimLen = trimStr.length();
        int strLen = str.length();
        if (strLen != 0 && trimLen != 0) {
            while (strLen != 0 && str.substring(strLen - trimLen, strLen).equals(trimStr)) {
                str = str.delete(strLen - trimLen, strLen);
                strLen = str.length();
            }
        }
    }
    return str;
}

left trim (lTrim)

public StringBuilder lTrim(StringBuilder str, String trimStr) {
    if (str != null && trimStr != null) {
        int len = trimStr.length();
        if (str.length() != 0 && len != 0) {
            while (str.length() != 0 && str.substring(0, len).equals(trimStr)) {
                str = str.delete(0, len);
            }
        }
    }
    return str;
}

Upvotes: 4

Riiverside
Riiverside

Reputation: 798

Something like this could work:

private StringBuilder rtrim(StringBuilder str, String trimStr) {
    if(str.length() == 0 || trimStr.isEmpty()) {
        return str;
    }
    int lastIndexOf = str.lastIndexOf(trimStr);

    if(lastIndexOf >= 0 && lastIndexOf + trimStr.length() == str.length()) {
        str.setLength(lastIndexOf);
    }
    return str;
}

This will remove trimStr from the end of the provided str. Using lastIndexOf directly on the StringBuilder avoids converting everything to a string.

If you want to remove all occurrences of trimStr at the end of str you can do something like this:

private StringBuilder rtrim(StringBuilder str, String trimStr) {
    if(str.length() == 0 || trimStr.isEmpty()) {
        return str;
    }
    int lastIndexOf;
    while((lastIndexOf = str.lastIndexOf(trimStr)) >= 0 && lastIndexOf + trimStr.length() == str.length()) {
        str.setLength(lastIndexOf);
    }
    return str;
}

Upvotes: 0

Madushan Perera
Madushan Perera

Reputation: 2598

As you have mentioned, you can use Apache StringUtils library :

private static StringBuilder rTrim(StringBuilder sb, String stripChars) {
    return new StringBuilder(StringUtils.stripEnd(sb.toString(), stripChars));
}

private static StringBuilder lTrim(StringBuilder sb, String stripChars) {
    return new StringBuilder(StringUtils.stripStart(sb.toString(), stripChars));
}

Upvotes: 0

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