How to trim the whitespace from a string? [duplicate]

Answer 1

Apache StringUtils.strip is the best answer here that works with all expected white space characters (not just space), and can be downloaded here:

Here's the relevant code ripped from this source file to implement it in your own class if you wanted, but really, just download and use StringUtils to get more bang for your buck! Note that you can use StringUtils.stripStart to trim any leading character from a java string as well.

public static final int INDEX_NOT_FOUND = -1

public static String strip(final String str) {
    return strip(str, null);
}

public static String stripStart(final String str, final String stripChars) {
    int strLen;
    if (str == null || (strLen = str.length()) == 0) {
        return str;
    }
    int start = 0;
    if (stripChars == null) {
        while (start != strLen && Character.isWhitespace(str.charAt(start))) {
            start++;
        }
    } else if (stripChars.isEmpty()) {
        return str;
    } else {
        while (start != strLen && stripChars.indexOf(str.charAt(start)) != INDEX_NOT_FOUND) {
            start++;
        }
    }
    return str.substring(start);
}

public static String stripEnd(final String str, final String stripChars) {
    int end;
    if (str == null || (end = str.length()) == 0) {
        return str;
    }

    if (stripChars == null) {
        while (end != 0 && Character.isWhitespace(str.charAt(end - 1))) {
            end--;
        }
    } else if (stripChars.isEmpty()) {
        return str;
    } else {
        while (end != 0 && stripChars.indexOf(str.charAt(end - 1)) != INDEX_NOT_FOUND) {
            end--;
        }
    }
    return str.substring(0, end);
}

public static String strip(String str, final String stripChars) {
    if (isEmpty(str)) {
        return str;
    }
    str = stripStart(str, stripChars);
    return stripEnd(str, stripChars);
}

Answer 2

If you don't want to use String.trim() method, then it can be implemented like below. The logic will handle different scenarios like space, tab and other special characters.

public static String trim(String str){
    int i=0;
    int j = str.length();
    char[] charArray = str.toCharArray();
    while((i<j) && charArray[i] <=' '){
        i++;
    }
    while((i<j) && charArray[j-1]<= ' '){
        j--;
    }
    return str.substring(i, j+1);

}

public static void main(String[] args) {
    System.out.println(trim("    abcd ght trip              "));

}