Develop code to declare variables to store reference types.

Consider this code segment that declares and initializes reference variables:

ArrayList<String> list1 = new ArrayList<String>();
ArrayList<String> list2 = new ArrayList<String>();
ArrayList<String> list3 = list1;

list1.add("Java");
list2.add("Python");
list3.add("C++");

After this code executes, what is the size of the ArrayList referenced by list1?