将数组转换为List

String str = "1,1,,2,2,";
String str2 = "1,2,3";
//第一种转换
List list1 = Arrays.asList(str.split(","));
List list2 = Arrays.asList(str2.split(","));

//第二种转换
List list1 = new ArrayList(Arrays.asList(str.split(",")));
List list2 = new ArrayList(Arrays.asList(str2.split(",")));

System.out.println(list1.size());
for(int i=0;i<list1.size();i++){
System.out.println(list1.get(i));
}
//List list3 = list2.retainAll(list1);
for(int i=0;i<list2.size();i++){
System.out.println(list2.get(i));
}

//用第一种会出错，必须转换为第二种
list1.retainAll(list2);