Recently in learning Java8 CompletableFuture class, want to learn the multithreading,
Also try to write some code, deficiencies still please people more directions!

 import Java. IO. IOException; 
Import the Java. Nio. File. FileSystems; 
Import the Java. Nio. File. FileVisitResult; 
Import the Java. Nio. File. The Files; 
Import the Java. Nio. File. The Path; 
Import the Java. Nio. File. Paths; 
Import the Java. Nio. File. SimpleFileVisitor; 
Import the Java. Nio. File. The attribute. The BasicFileAttributes; 
import java.util.ArrayList; 
Import the Java. Util. Collections; 
import java.util.List; 
Import the Java. Util. Objects; 
The import java.util.concurrent.Com pletableFuture; 
Import the Java. Util. Concurrent. The ExecutorService; 
Import the Java. Util. Concurrent. Executors; 
Import the Java. Util. Concurrent. TimeUnit; 

Public class Test {
Private static final ExecutorService serivce=Executors. NewFixedThreadPool (Runtime. The getRuntime (). AvailableProcessors ()); 

The public Test () {
//TODO Auto - generated constructor stub 
} 

Private static List ExecFileCopy (String SRC, String tar) {
List LST=Collections. SynchronizedList (new ArrayList ()); 

Try {
The Path target=FileSystems. GetDefault (.) getPath (tar); 
Files. The walkFileTree (Paths. The get (SRC), new SimpleFileVisitor () {
Public FileVisitResult preVisitDirectory (Path dir, BasicFileAttributes attrs) throws IOException {
Objects. RequireNonNull (dir); 
Objects. RequireNonNull (attrs); 
The Path targetPath=target. Resolve (dir. Subpath (0, dir. GetNameCount ())); 
Files. CreateDirectories (targetPath); 
Return FileVisitResult. CONTINUE; 
} 

Public FileVisitResult visitFile (Path file, BasicFileAttributes attrs) throws IOException {
Objects. RequireNonNull (file); 
The Path targetPath=target. Resolve (file. Subpath (0, the file. GetNameCount ())); 
LST. Add (CompletableFuture. RunAsync (() - & gt; {
Try {
Files. The copy (file, targetPath); 
} the catch (IOException e) {
//TODO Auto - generated the catch block, 
E.p rintStackTrace (); 
} 
}, serivce)); 
Return FileVisitResult. CONTINUE; 
} 
}); 
} the catch (IOException e) {
E.p rintStackTrace (); 
} 
Return LST. 
} 

Public static void main (String [] args) throws the Exception {
Long s=System. CurrentTimeMillis (); 
String tar="E: \ \ 3"; 
String SRC="F: \ \ angular2";//directory contains 386 m 734 m size file (1), 185 m files (1), the remaining 26918 files for grade K pieces file 

List List=execFileCopy (SRC, tar); 
CompletableFuture ControlFuture=CompletableFuture. AllOf (list. ToArray (new CompletableFuture [] {})); 
while(! ControlFuture. IsDone () {} 
System. The out. Println (" exception found: "+ controlFuture. IsCompletedExceptionally ()); 

System. The out. Println ((System. CurrentTimeMillis () - s)/1000);//takes 27 seconds system environment (i5-3337 - u 4 g 256 GSSD ramdisk Win10) 
} 
}