code: public static String getNestedString(String str, String open, String close) {
        return substringBetween(str, open, close);
    }
docs: <p>Gets the String that is nested in between two Strings.
  Only the first match is returned.</p>
  
  <p>A <code>null</code> input String returns <code>null</code>.
  A <code>null</code> open/close returns <code>null</code> (no match).
  An empty ("") open/close returns an empty string.</p>
  
  <pre>
  GosuStringUtil.getNestedString(null, *, *)          = null
  GosuStringUtil.getNestedString("", "", "")          = ""
  GosuStringUtil.getNestedString("", "", "tag")       = null
  GosuStringUtil.getNestedString("", "tag", "tag")    = null
  GosuStringUtil.getNestedString("yabcz", null, null) = null
  GosuStringUtil.getNestedString("yabcz", "", "")     = ""
  GosuStringUtil.getNestedString("yabcz", "y", "z")   = "abc"
  GosuStringUtil.getNestedString("yabczyabcz", "y", "z")   = "abc"
  </pre>
  
  @param str  the String containing nested-string, may be null
  @param open  the String before nested-string, may be null
  @param close  the String after nested-string, may be null
  @return the nested String, <code>null</code> if no match
  @deprecated Use the better named {@link #substringBetween(String, String, String)}.
  Method will be removed in Commons Lang 3.0.