public void testDefaultString() {
        assertThat(StringUtil.defaultString(null), is(""));
        assertThat(StringUtil.defaultString(""), is(""));
        assertThat(StringUtil.defaultString("aaa"), is("aaa"));
    }

    /**
     *
     */
    @Test
    public void testDefaultStringDefaultStr() {
        assertThat(StringUtil.defaultString(null, "NULL"), is("NULL"));

     * <p>
     * Usage example:
     * </p>
     *
     * <pre>
     * StringUtil.defaultString(null, "NULL")  = "NULL"
     * StringUtil.defaultString("", "NULL")    = ""
     * StringUtil.defaultString("aaa", "NULL") = "aaa"
     * StringUtil.defaultString("aaa", null)   = "aaa"
     * StringUtil.defaultString(null, null)    = null
     * </pre>
     *
     * @param str