try writing into the method

1, this Lists.newArrayList method is encapsulated by yourself, isn't it without generics? Even if you use list < user > to receive, the original type is still obj

2, using lists in the toolkit, generic parameters, and native arraylist are all fine

3, run result

I have tried. You can visit the getName () method

partial code

filter
<ol>
<li>1 2 1+2FunctionalInterface
</li>
<li>1 1 1+1FunctionalInterface
</li>
</ol>
ComparatorBiFunction
int compare(T o1, T o2);
 isn't this pattern  BiFunction , just saying that the two are different  FunctionalInterface , just like  BinaryOperator  and  BiFunction 
 so when you call the filter method with the same type  User , both methods actually match, so the third parameter cannot be inferred, only the  Object  type is the default 
.
 suppose you create a new type  UserNew , which is similar to the  User  type. If you call the filter method with two different type parameters, you must have used the first one, so that you will not make a mistake 
.
final List<User> users1 = Lists.newArrayList(new User("rx", 17), new User("haor", 15));
final List<User> users2 = Lists.newArrayList(new User("Ling", 15), new User("rx", 17));
final List<UserNew> users3 = Lists.newArrayList(new UserNew("Ling", 15), new UserNew("rx", 17));

// getName 
ListUtil.filter(users1, users2, (u1, u2) -> Objects.equals(u1.getName(), u2.getName()));
// getName 
ListUtil.filter(users1, users3, (u1, u2) -> Objects.equals(u1.getName(), u2.getName()));

 of course, the subject will definitely say, "I also have scenarios in which method 1 is called with the same type, so you need to specify the third parameter type 
, such as the example of the subject. Finally, you should write 
."
// BiFunction
BiFunction<User, User, Boolean> biFunction = (u1, u2) -> Objects.equals(u1.getName(), u2.getName());
ListUtil.filter(users1, users2, biFunction);

 the above is for reference only ((OO) OO)