#fixed code
                             @Test
	public void testJoinString() throws RiotApiException {
		// Valid Usage for Strings
		assertEquals("abc", Convert.joinString(",", "abc"));
		assertEquals("abc,def,ghi", Convert.joinString(",", "abc", "def", "ghi"));
		// Valid Usage for other objects
		assertEquals("RANKED_SOLO_5x5,TEAM_BUILDER_DRAFT_RANKED_5x5",
				Convert.joinString(",", QueueType.RANKED_SOLO_5x5, QueueType.TEAM_BUILDER_DRAFT_RANKED_5x5));
		assertEquals("info,lore", Convert.joinString(",", ChampData.INFO, ChampData.LORE));
		// NullPointerException
		thrown.expect(NullPointerException.class);
		Convert.joinString(null, (CharSequence[]) null);
	}
#vulnerable code 
                             @Test
	public void testJoinString() throws RiotApiException {
		// Valid Usage
		assertEquals("abc", Convert.joinString(",", "abc"));
		assertEquals("abc,def,ghi", Convert.joinString(",", "abc", "def", "ghi"));
		// NullPointerException
		thrown.expect(NullPointerException.class);
		Convert.joinString(null, (CharSequence[]) null);
	} 
                            #location 8 
                            #vulnerability type NULL_DEREFERENCE