list.add并不是copy

Preference preference = new Preference();

preference.setParentId(1);
preference.setPreferenceDescription("11");
preference.setPreferenceId(11);

List<Preference> list = new ArrayList<>();

list.add(preference);
for(Preference p:list) {
System.out.println(p.getPreferenceName());
}
preference.setPreferenceName("111");

for(Preference p:list) {
System.out.println(p.getPreferenceName());
}