@Override
    public Object get(int i, int j) {
        return df.get(index[i], j);
    }
@Test
    public void testGet() {
        System.out.println("get");
        System.out.println(df);
        System.out.println(df.get(0));
        System.out.println(df.get(1));
        assertEquals(48, df.getInt(0, 0));
        assertEquals("Jane", df.getString(0, 3));
        assertEquals(230000., df.get(0, 4));
        assertEquals(23, df.getInt(1, 0));
        assertEquals("Bob", df.getString(1, 3));
        assertNull(df.get(1, 4));
        assertEquals(13, df.getInt(2, 0));
        assertEquals("Amy", df.getString(2, 3));
        assertNull(df.get(2, 4));
        assertEquals(48, df.getInt(3, 0));
        assertEquals("Jane", df.getString(3, 3));
        assertEquals(230000., df.get(3, 4));
    }