Example of using nio2 to copy files in Java

This program is just created to make it easier to copy files (folders). 1. There is no need to create a new folder, which is as simple as copy and paste in windows. 2. There is a simple error reconnection mechanism 3 Duplicate copies are not required and files are differentially copied. 4. When copying folders, you can not copy the full path, but only focus on the folders that need to be copied. 5. The procedure has made a simple and necessary inspection, and the efficiency is not low. 6. The new API of nio2 of 7 is used.