问题
When list.addAll(list2) is called will objects in lists be copied to list? or just copy their references... did not find any explanation on javadoc...
回答1:
No copy of the objects or their data are made; their references are simply added to the list object.
回答2:
No, the objects will not be copied; references to the same objects will be added to the list.
回答3:
In general, java will not copy objects when you "add all", that is, for objects, pointers to the originals are used.
* But be careful ! For strings, due to immutability, an array copy will not point to the original string values, and you must not expect that changing a pointer to a string that was added to an array list will result in a new value inside the array list.
来源：https://stackoverflow.com/questions/7924887/will-addall-function-in-java-make-a-copy