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

The best way in my opinion:

public static String trimEnd(String source) {
    int pos = source.length() - 1;
    while ((pos >= 0) && Character.isWhitespace(source.charAt(pos))) {
        pos--;
    }
    pos++;
    return (pos < source.length()) ? source.substring(0, pos) : source;
}

This does not allocate any temporary object to do the job and is faster than using a regular expression. Also it removes all whitespaces, not just ' '.

Answer 2

This code is intended to be read a easily as possible by using descriptive names (and avoiding regular expressions).

It does use Java 8's Optional so is not appropriate for everyone.

public static String removeTrailingWhitspace(String string) {
    while (hasWhitespaceLastCharacter(string)) {
        string = removeLastCharacter(string);
    }
    return string;
}

private static boolean hasWhitespaceLastCharacter(String string) {
    return getLastCharacter(string)
            .map(Character::isWhitespace)
            .orElse(false);
}

private static Optional<Character> getLastCharacter(String string) {
    if (string.isEmpty()) {
        return Optional.empty();
    }
    return Optional.of(string.charAt(string.length() - 1));
}

private static String removeLastCharacter(String string) {
    if (string.isEmpty()) {
        throw new IllegalArgumentException("String must not be empty");
    }
    return string.substring(0, string.length() - 1);
}

Answer 3

The most practical answer is @Micha's, Ahmad's is reverse of what you wanted so but here's what I came up with in case you'd prefer not to use unfamiliar tools or to see a concrete approach.

public String trimEnd( String myString ) {

    for ( int i = myString.length() - 1; i >= 0; --i ) {
        if ( myString.charAt(i) == ' ' ) {
            continue;
        } else {
            myString = myString.substring( 0, ( i + 1 ) );
            break;
        }
    }
    return myString;
}

Used like:

public static void main( String[] args ) {

    String s = "    Some text here   ";
    System.out.println( s + "|" );
    s = trimEnd( s );
    System.out.println( s + "|" );
}

Output:

Some text here   |
Some text here|

Answer 4

As of JDK11 you can use stripTrailing:

String result = str.stripTrailing();

Answer 5

Spring framework gives a useful org.springframework.util.StringUtils.

trimTrailingWhitespace

Answer 6

Another option is to use Apache Commons StringUtils, specifically StringUtils.stripEnd

String stripped = StringUtils.stripEnd("   my lousy string    "," ");