public static String underScoreToCamelCase(String key) {
        if (key.isEmpty())
            return key;

        StringBuilder sb = new StringBuilder(key.length());
        for (int i = 0; i < key.length(); i++) {
            char c = key.charAt(i);
            if (c == '_') {
                i++;
                if (i < key.length())
                    sb.append(Character.toUpperCase(key.charAt(i)));
                else
                    sb.append(c);
            } else
                sb.append(c);
        }

        return sb.toString();
    }
@Test
    public void testUnderscoreToCamelCase() {
        assertEquals("testCase", Helper.underScoreToCamelCase("test_case"));
        assertEquals("testCaseTBD", Helper.underScoreToCamelCase("test_case_t_b_d"));
        assertEquals("TestCase_", Helper.underScoreToCamelCase("_test_case_"));
    }