Question

2. public static string trim(String str) This method should take a string str and use recursion to return a string in which any leading and/or trailing spaces in the original string are removed. For example: trim(" hello world ") should return the string "hello world" trim("recursion ") should return the string "recursion" The String class comes with a built-in trim() method that does the same thing as the method that we're asking you to write; you may not use that method in your solution! Special cases: If the parameter is null, the method should return null. If the parameter is the empty string, the method should return the empty string

Answer 1

public static String trim(String str) {
    if (str == null || str.isEmpty())
        return str;
    String result = "";
    int index = str.length() - 1;
    while (index >= 0) {
        if (!Character.isSpaceChar(str.charAt(index))) {
            break;
        }
        index--;
    }
    for (int i = 0; i <= index; i++) {
        if (!Character.isSpaceChar(str.charAt(i)) || result.length() > 0) {
            result += str.charAt(i);
        }
    }
    return result;
}