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public class Answer87 {
    public static String formatCenter(String str, int length) {
        if (length <= 0) return str;
        StringBuilder builder = new StringBuilder(str);
        for (int index = 0; index < length; index++) {
            builder.insert(0, ' ');
            builder.append(' ');
        }
        int start = (builder.length() - length) / 2;
        return builder.substring(start, start + length);
    }

    public static void main(String[] args) {
        System.out.println(formatCenter("abcde", 5));    // "abcde"
        System.out.println(formatCenter("abcde", 7));    // " abcde "
        System.out.println(formatCenter("abcde", 8));    // "  abcde "
        System.out.println(formatCenter("abcde", 1));    // "c"
        System.out.println(formatCenter("abcde", 2));    // "bc"
        System.out.println(formatCenter("abcde", 0));    // "abcde"
    }
}