### Question:
Strings { public static String rightTrim(String str) { if (str == null) { return null; } if (str.length() == 0) { return EMPTY_STRING; } int j = str.length(); for (int i = str.length() - 1; i >= 0; --i) { if (Character.isWhitespace(str.charAt(i))) { j--; } else { break; } } return str.substring(0, j); } private  Strings(); static boolean isNullOrEmpty(String str); static boolean hasText(String s); static boolean allHasText(String... strings); static boolean allNullOrEmpty(String... strings); static String leftTrim(String s); static String rightTrim(String str); static boolean containsNone(String str, String invalidCharsStr); static boolean containsOnly(String str, String allowedChars); static String repeat(char c, int count); static String repeat(String str, int count); static String reverse(String str); static String insertFromLeft(String str, int interval, String stringToInsert); static String insertFromRight(String str, int interval, String stringToInsert); static String rightPad(String str, int size); static String rightPad(String str, int size, char padChar); static String rightPad(String str, int size, String padStr); static String leftPad(String str, int size); static String leftPad(String str, int size, char padChar); static String subStringUntilFirst(String str, String s); static String subStringUntilLast(String str, String s); static String subStringAfterFirst(String str, String s); static String subStringAfterLast(String str, String s); static String leftPad(String str, int size, String padStr); static String whiteSpacesToSingleSpace(String str); static String eliminateWhiteSpaces(String str); static String[] separateGrams(String word, int gramSize); static final String EMPTY_STRING; static final String[] EMPTY_STRING_ARRAY; }### Answer:
@Test public void rightTrimTest() { assertNull(rightTrim(null)); assertEquals(rightTrim(""), ""); assertEquals(rightTrim(" \t"), ""); assertEquals(rightTrim("aaa "), "aaa"); assertEquals(rightTrim("aaa \t "), "aaa"); assertEquals(rightTrim("aaa\n "), "aaa"); assertEquals(rightTrim("aaa"), "aaa"); assertEquals(rightTrim(" 123 "), " 123"); assertEquals(rightTrim(" 3 123 \t"), " 3 123"); }