What does it mean when we say an ArrayList is not synchronized?

Question

What does it mean when we say an ArrayList is not synchronized?

Does it mean that if we declare an ArrayList in object scope, multiple threads accessing the objects hav

Answer 1

Being synchronized means that every operation is thread safe - if you use the same Array List from two threads at the same time, they can't corrupt the state. However, this makes it slower.

By default ArrayList is not synchronized, you can achieved that by synchronized keyword

ArrayList al=new ArrayList();

Collections.synchronized(al);