How to trim the whitespace from a string?

user_458442 0
Viewed 60057

I am writing this function for a J2ME application, so I don't have some of the more advanced / modern Java classes available to me. I am getting java.lang.ArrayIndexOutOfBoundsException on this. So, apparently either it doesn't like the way I've initialized the newChars array, or I'm not doing something correctly when calling System.arraycopy.

/*
 * remove any leading and trailing spaces
 */
public static String trim(String str) {
    char[] chars = str.toCharArray();
    int len = chars.length;
    // leading
    while ( (len > 0 ) && ( chars[0] == ' ' ) ) {
        char[] newChars = new char[] {}; // initialize empty array
        System.arraycopy(chars, 1, newChars, 0, len - 1);
        chars = newChars;
        len = chars.length;
    }
    // TODO: trailing
    return chars.toString();
}
java-me java
8 Answers

With JDK/11, now you can make use of the String.strip API to return a string whose value is this string, with all leading and trailing whitespace removed. The javadoc for the same is :

/**
 * Returns a string whose value is this string, with all leading
 * and trailing {@link Character#isWhitespace(int) white space}
 * removed.
 * <p>
 * If this {@code String} object represents an empty string,
 * or if all code points in this string are
 * {@link Character#isWhitespace(int) white space}, then an empty string
 * is returned.
 * <p>
 * Otherwise, returns a substring of this string beginning with the first
 * code point that is not a {@link Character#isWhitespace(int) white space}
 * up to and including the last code point that is not a
 * {@link Character#isWhitespace(int) white space}.
 * <p>
 * This method may be used to strip
 * {@link Character#isWhitespace(int) white space} from
 * the beginning and end of a string.
 *
 * @return  a string whose value is this string, with all leading
 *          and trailing white space removed
 *
 * @see Character#isWhitespace(int)
 *
 * @since 11
 */
public String strip()

The sample cases for these could be:--

System.out.println("".strip());
System.out.println("  both  ".strip());
System.out.println("  leading".strip());
System.out.println("trailing  ".strip());
user_17461180

You can use Guava CharMatcher.

String outputString = CharMatcher.whitespace().trimFrom(inputString);

Note: This works because whitespace is all in the BMP.

user_14071700
Related