#vulnerable code 
                                public void testDecodePadOnly() {
        assertTrue(Base64.decodeBase64("====".getBytes()).length == 0);
        assertEquals("", new String(Base64.decodeBase64("====".getBytes())));
        // Test truncated padding
        assertTrue(Base64.decodeBase64("===".getBytes()).length == 0);
        assertTrue(Base64.decodeBase64("==".getBytes()).length == 0);
        assertTrue(Base64.decodeBase64("=".getBytes()).length == 0);
        assertTrue(Base64.decodeBase64("".getBytes()).length == 0);
    } 
                            #location 2 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                public void testDecodePadOnly() throws UnsupportedEncodingException {
        assertTrue(Base64.decodeBase64("====".getBytes("UTF-8")).length == 0);
        assertEquals("", new String(Base64.decodeBase64("====".getBytes("UTF-8"))));
        // Test truncated padding
        assertTrue(Base64.decodeBase64("===".getBytes("UTF-8")).length == 0);
        assertTrue(Base64.decodeBase64("==".getBytes("UTF-8")).length == 0);
        assertTrue(Base64.decodeBase64("=".getBytes("UTF-8")).length == 0);
        assertTrue(Base64.decodeBase64("".getBytes("UTF-8")).length == 0);
    }