#vulnerable code 
                                @Test
    public void capitalizeTest()
    {

        assertEquals(capitalize("hola mundo abc"), "Hola mundo abc");
        assertEquals(capitalize("HOLA mundO AbC"), "Hola mundo abc");
        assertEquals(capitalize("Hola Mundo abC"), "Hola mundo abc");
        assertEquals(capitalize(""), "");
        assertEquals(capitalize("* Hola Mundo aBC"), "* hola mundo abc");

        assertEquals(capitalize("iyi akşamlar", new Locale("tr")), "İyi akşamlar");

        try
        {
            capitalize(null);
            fail("handles null?");
        } catch (NullPointerException ex)
        {

        }

    } 
                            #location 15 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @Test
    public void capitalizeTest()
    {

        assertEquals(capitalize("hola mundo abc"), "Hola mundo abc");
        assertEquals(capitalize("HOLA mundO AbC"), "Hola mundo abc");
        assertEquals(capitalize("Hola Mundo abC"), "Hola mundo abc");
        assertEquals(capitalize(" Hola Mundo abC  "), "Hola mundo abc");
        assertEquals(capitalize(" (hola Mundo abC)  "), "(Hola mundo abc)");
        assertEquals(capitalize("[HOLA Mundo abC]"), "[Hola mundo abc]");
        assertEquals(capitalize("-HOLA Mundo abC-"), "-Hola mundo abc-");
        assertEquals(capitalize(" ~.-(HOLA Mundo abC)-.~"), "~.-(Hola mundo abc)-.~");
        assertEquals(capitalize(""), "");
        assertEquals(capitalize("* Hola Mundo aBC"), "* Hola mundo abc");
        assertEquals(capitalize("2020"), "2020");

        assertEquals(capitalize("iyi akşamlar", new Locale("tr")), "İyi akşamlar");

        try
        {
            capitalize(null);
            fail("handles null?");
        } catch (NullPointerException ex)
        {

        }

    }