#fixed code
                                @Test
    public void firstOrNull() {
        final Integer result = $.firstOrNull(asList(5, 4, 3, 2, 1));
        assertEquals("5", result.toString());
        final Integer resultObj = new $<Integer>(asList(5, 4, 3, 2, 1)).firstOrNull();
        assertEquals("5", resultObj.toString());
        final Integer resultChain = $.chain(asList(5, 4, 3, 2, 1)).firstOrNull().item();
        assertEquals("5", resultChain.toString());
        assertNull($.firstOrNull(Collections.emptyList()));
        assertNull(new $<Integer>(Collections.<Integer>emptyList()).firstOrNull());
        final int resultPred = $.firstOrNull(asList(5, 4, 3, 2, 1), new Predicate<Integer>() {
            public Boolean apply(Integer item) {
                return item % 2 == 0;
            }
        });
        assertEquals(4, resultPred);
        final int resultPredChain = $.chain(asList(5, 4, 3, 2, 1)).firstOrNull(new Predicate<Integer>() {
            public Boolean apply(Integer item) {
                return item % 2 == 0;
            }
        }).item();
        assertEquals(4, resultPredChain);
        assertNull($.firstOrNull(Collections.<Integer>emptyList(), new Predicate<Integer>() {
            public Boolean apply(Integer item) {
                return item % 2 == 0;
            }
        }));
        final int resultPredObj = new $<Integer>(asList(5, 4, 3, 2, 1)).firstOrNull(new Predicate<Integer>() {
            public Boolean apply(Integer item) {
                return item % 2 == 0;
            }
        });
        assertEquals(4, resultPredObj);
        assertNull(new $<Integer>(Collections.<Integer>emptyList()).firstOrNull(new Predicate<Integer>() {
            public Boolean apply(Integer item) {
                return item % 2 == 0;
            }
        }));
    }
#vulnerable code 
                                @Test
    public void firstOrNull() {
        final Integer result = $.firstOrNull(asList(5, 4, 3, 2, 1));
        assertEquals("5", result.toString());
        final Integer resultObj = new $<Integer>(asList(5, 4, 3, 2, 1)).firstOrNull();
        assertEquals("5", resultObj.toString());
        assertNull($.firstOrNull(Collections.emptyList()));
        assertNull(new $<Integer>(Collections.<Integer>emptyList()).firstOrNull());
        final int resultPred = $.firstOrNull(asList(5, 4, 3, 2, 1), new Predicate<Integer>() {
            public Boolean apply(Integer item) {
                return item % 2 == 0;
            }
        });
        assertEquals(4, resultPred);
        assertNull($.firstOrNull(Collections.<Integer>emptyList(), new Predicate<Integer>() {
            public Boolean apply(Integer item) {
                return item % 2 == 0;
            }
        }));
        final int resultPredObj = new $<Integer>(asList(5, 4, 3, 2, 1)).firstOrNull(new Predicate<Integer>() {
            public Boolean apply(Integer item) {
                return item % 2 == 0;
            }
        });
        assertEquals(4, resultPredObj);
        assertNull(new $<Integer>(Collections.<Integer>emptyList()).firstOrNull(new Predicate<Integer>() {
            public Boolean apply(Integer item) {
                return item % 2 == 0;
            }
        }));
    } 
                            #location 20 
                            #vulnerability type NULL_DEREFERENCE