하나의 파일 크기를 계산하는 몇 가지 실현 방식
30016 단어 파일 크기
import java.io.File;
/**
*
*/
public class TotalFileSizeSequential {
private long getTotalSizeOfFilesInDir(File file) {
if(file.isFile())
return file.length();
long length = 0;
File []children = file.listFiles();
if(children != null)
for(final File child : children) {
length += getTotalSizeOfFilesInDir(child);
}
return length;
}
public static void main(String[] args) {
final long start = System.nanoTime();
final File file = new File("C:\\Windows");
TotalFileSizeSequential total = new TotalFileSizeSequential();
long size = total.getTotalSizeOfFilesInDir(file);
final long end = System.nanoTime();
System.out.println("total size:" + size);
System.out.println("total token:"+(end - start) /1.0e9);
}
}2. 스레드 협업, 분자 작업, 새로운 스레드 시작(디렉터리가 깊지 않을 때 문제없음)
import java.io.File;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
/**
* ，
*
*
*/
public class NativelyConcurrentTotalFileSize {
private long getTotalSizeOfFile(File file) throws InterruptedException, ExecutionException, TimeoutException {
ExecutorService service = Executors.newFixedThreadPool(100);
long size = getTotalSizeOfFilesInDir(service, file);
return size;
}
private long getTotalSizeOfFilesInDir(final ExecutorService service, final File file) throws InterruptedException, ExecutionException, TimeoutException {
if(file.isFile())
return file.length();
long size = 0;
File []children = file.listFiles();
if(children != null) {
List<Future<Long>> futures = new ArrayList<Future<Long>>() ;
for(final File child : children)
futures.add(service.submit((new Callable<Long>() {
public Long call() throws Exception {
return getTotalSizeOfFilesInDir(service, child);
}
})
));
for(Future<Long> future : futures) {
size += future.get(10,TimeUnit.SECONDS);
}
return size;
}
return size;
}
public static void main(String[] args) throws InterruptedException, ExecutionException, TimeoutException {
final long start = System.nanoTime();
final File file = new File("C:\\Windows");
NativelyConcurrentTotalFileSize total = new NativelyConcurrentTotalFileSize();
long size = total.getTotalSizeOfFile(file);
final long end = System.nanoTime();
System.out.println("total size:" + size);
System.out.println("total token:"+(end - start) /1.0e9);
}
}3. 두 번째 방법에서 라인 잠금 시간이 초과되는 문제를 해결하고 폴더의 파일 크기와 메모리 하위 디렉터리를 계산할 때마다
import java.io.File;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
public class ConcurrentTotalFileSize {
/**
* （ ）
*/
class SubDirectoriesAndSize {
public long size;
public List<File> subDirectories;
public SubDirectoriesAndSize(final long size, final List<File> subDirectories) {
this.size = size;
this.subDirectories = Collections.unmodifiableList(subDirectories);
}
}
/**
*
*/
private long getTotalSizeOfFile(File file) throws InterruptedException, ExecutionException, TimeoutException {
ExecutorService service = Executors.newFixedThreadPool(100);
long size = getTotalSizeOfFilesInDir(service, file);
return size;
}
/**
*
*/
private SubDirectoriesAndSize getSubDirectoriesAndSize(final File file) {
long total = 0;
List<File> subDirectories = new ArrayList<File>();
if(file.isDirectory()) {
File []children = file.listFiles();
if(children != null)
for(final File child : children) {
if(child.isFile())
total += child.length();
else
subDirectories.add(child);
}
}
return new SubDirectoriesAndSize(total, subDirectories);
}
private long getTotalSizeOfFilesInDir(ExecutorService service, File file) throws InterruptedException, ExecutionException, TimeoutException {
if(file.isFile())
return file.length();
long size = 0;
List<File> directories = new ArrayList<File>();
directories.add(file);
try {
while(!directories.isEmpty()) {
List<Future<SubDirectoriesAndSize>> futures = new ArrayList<Future<SubDirectoriesAndSize>>() ;
for(final File child : directories) {
futures.add(service.submit(new Callable<SubDirectoriesAndSize>() {
@Override
public SubDirectoriesAndSize call() throws Exception {
return getSubDirectoriesAndSize(child);
}
}));
}
directories.clear();//
for(Future<SubDirectoriesAndSize> future : futures) {
size += future.get().size;
directories.addAll(future.get(100,TimeUnit.SECONDS).subDirectories);
}
}
} finally {
service.shutdown();
}
return size;
}
public static void main(String[] args) throws InterruptedException, ExecutionException, TimeoutException {
final long start = System.nanoTime();
final File file = new File("C:\\Windows");//
ConcurrentTotalFileSize total = new ConcurrentTotalFileSize();
long size = total.getTotalSizeOfFile(file);
final long end = System.nanoTime();
System.out.println("total size:" + size);
System.out.println("total token:"+(end - start) /1.0e9);
}
}4. 데이터 교환, Array BlockingQueue를 사용하여 온라인 거리에서 여러 그룹의 데이터를 상호 발송
import java.io.File;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.concurrent.atomic.AtomicLong;
/**
*
* ArrayBlockingQueue，
*/
public class ConcurrentTotalFileSizeWQueue {
private ExecutorService service;
final private BlockingQueue<Long> fileSizes = new ArrayBlockingQueue<Long>(500);//
final private AtomicLong pendingFileVisits = new AtomicLong();
private long getTotalSizeOfFile(File file) throws InterruptedException {
service = Executors.newFixedThreadPool(100);
try {
startExploreFile(file);
long totalSize = 0;
while(pendingFileVisits.get() > 0 || fileSizes.size() > 0) {
final long size = fileSizes.poll(10, TimeUnit.SECONDS);
totalSize += size;
}
return totalSize;
} finally {
service.shutdown();
}
}
private void startExploreFile(final File file) {
pendingFileVisits.incrementAndGet();
service.execute(new Runnable() {
public void run() {
exploreDir(file);
}
});
}
private void exploreDir(final File file) {
long fileSize = 0;
if(file.isFile())
fileSize = file.length();
else {
File[] children = file.listFiles();
if(children != null) {
for(File child : children) {
if(child.isFile())
fileSize += child.length();
else
startExploreFile(child);
}
}
}
try {
fileSizes.put(fileSize);
} catch (InterruptedException e) {
e.printStackTrace();
}
pendingFileVisits.decrementAndGet();
}
public static void main(String[] args) throws InterruptedException, ExecutionException, TimeoutException {
final long start = System.nanoTime();
final File file = new File("C:\\Windows");//
ConcurrentTotalFileSizeWQueue total = new ConcurrentTotalFileSizeWQueue();
long size = total.getTotalSizeOfFile(file);
final long end = System.nanoTime();
System.out.println("total size:" + size);
System.out.println("total token:"+(end - start) /1.0e9);
}
}5, CountDownLatch 구현, 결과를 반환하지 않음, 공유 상태, 코드 간결
/**
* CountDownLatch
* ，AtomicLong long
* java.util.concurrent.atomic
*/
public class ConcurrentTotalSizeWLatch {
private ExecutorService service;
private AtomicLong pendingFileVisits = new AtomicLong();// （ ）
private AtomicLong totalSize = new AtomicLong();//
private CountDownLatch latch = new CountDownLatch(1);
private long getTotalSizeOfFile(File file) {
service = Executors.newFixedThreadPool(100);
pendingFileVisits.incrementAndGet();
updateTotalSizeOfFileInDir(file);
try {
latch.await(100, TimeUnit.SECONDS);// latch 0，
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
service.shutdown();
}
return totalSize.longValue();
}
private void updateTotalSizeOfFileInDir(File file) {
long fileSize = 0;
if(file.isFile())
fileSize = file.length();
if(file.isDirectory()) {
File[] children = file.listFiles();
if(children != null) {
for(final File child : children) {
if(file.isFile())
fileSize += child.length();
else {
pendingFileVisits.incrementAndGet();
service.execute(new Runnable() {
public void run() {
updateTotalSizeOfFileInDir(child);
}
});
}
}
}
}
totalSize.addAndGet(fileSize);
if(pendingFileVisits.decrementAndGet() == 0) latch.countDown();//
}
public static void main(String[] args) {
final long start = System.nanoTime();
final File file = new File("C:\\Windows");
ConcurrentTotalSizeWLatch total = new ConcurrentTotalSizeWLatch();
long size = total.getTotalSizeOfFile(file);
final long end = System.nanoTime();
System.out.println("total size:" + size);
System.out.println("total token:"+(end - start) /1.0e9);
}이 학습 내용은
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