public foo() { first = new T(); second = new T(); } //ERROR

foo<String> f = foo.makeFoo(String::new)

public static <T> foo<T> makeFoo(Supplier<T> constr)
{
    return new foo<>(constr.get(), constr.get());
}

Error:(35, 38) java: method makeFoo in class generic.foo<T> cannot be applied to given types;
required: java.util.function.Supplier<T>
found: Integer::new
reason: cannot infer type-variable(s) T
(argument mismatch; incompatible parameter types in method reference)