java shallow vs. deep copy (to be solved)

1. What is shallow copy, what is a deep copy?

 

2.storm parallelism problem that requires the use of global variables static ConcorrentHashMap, because the addition of static, all threads can only copy a single copy of the global variables, operation, other threads can only wait for the thread to handle the operation is complete copy, i.e., the copy operation to achieve a single-threaded, threads are safe; without static, multiple copies can be copied, a copy of each thread copy after the copy operation, the copy data is then assigned to the original object . 

This copy is a deep copy or a shallow copy?

 

to be solved. . .