### Question:
TextTools { public static String removeControlChars(String text) { StringBuilder sb= new StringBuilder(); for (int i=0, n=StringUtils.length(text) ; i<n; i++) { char ch= text.charAt(i); if (ch < ' ') ch= ' '; sb.append(ch); } return sb.toString(); }  static String dquoteAround(String value); static boolean isQuote(char quote); static String removeControlChars(String text);  }### Answer:
@Test public void testRemoveControlChars() { assertEquals("", TextTools.removeControlChars(null)); assertEquals("", TextTools.removeControlChars("")); assertEquals(" ", TextTools.removeControlChars(" ")); assertEquals(" ", TextTools.removeControlChars(" \t\n ")); }