一 ByteBuffer
1 API使用案例
1.1 使用方式
- 向 buffer 写入数据，例如调用 channel.read(buffer)
- 调用 flip() 切换至读模式
- flip会使得buffer中的limit变为position，position变为0
- 从 buffer 读取数据，例如调用 buffer.get()
- 调用 clear() 或者compact()切换至写模式
- 调用clear()方法时position=0，limit变为capacity
- 调用compact()方法时，会将缓冲区中的未读数据压缩到缓冲区前面
- 重复以上步骤
1.2 使用ByteBuffer读取文件中的内容
public class ByteBufferTest {
public static void main(String[] args) {
// 获得FileChannel
try (FileChannel channel = new FileInputStream("data.txt").getChannel()) {
// 获得缓冲区
ByteBuffer buffer = ByteBuffer.allocate(10);
int hasNext = 0;
StringBuilder sb = new StringBuilder();
while ((hasNext = channel.read(buffer))>0){
// 切换读模式
buffer.flip();
// 当buffer中还有数据时，获取其中的数据
while (buffer.hasRemaining()){
sb.append((char)buffer.get());
}
// 切换写模式
buffer.clear();
}
System.out.println(sb.toString());
} catch (IOException e) {
e.printStackTrace();
}
}
}
- result
0123456789abcdef
2 内部结构
2.1 核心属性解读
字节缓冲区的父类Buffer中有几个核心属性
- capacity：缓冲区的容量。通过构造函数赋予，一旦设置，无法更改
- limit：缓冲区的界限。位于limit 后的数据不可读写。缓冲区的限制不能为负，并且不能大于其容量
- position：下一个读写位置的索引。缓冲区的位置不能为负，并且不能大于limit
- mark：记录当前position的值。position被改变后，可以通过调用reset() 方法恢复到mark的位置。
// Invariants: mark <= position <= limit <= capacity
private int mark = -1;
private int position = 0;
private int limit;
private int capacity;
2.2 API调用对核心属性的修改
- put()方法
- put()方法可以将一个数据放入到缓冲区中。
- 进行该操作后，postition的值会+1，指向下一个可以放入的位置。capacity = limit ，为缓冲区容量的值。
20201109145709.png
- flip()方法
- flip()方法会切换对缓冲区的操作模式，由写->读
- 进行该操作后 position = 0 ， limit 指向最后一个元素的下一个位置，capacity不变
20201109145753.png
- get()方法
- get()方法会读取缓冲区中的一个值
- 进行该操作后，position会+1，如果超过了limit则会抛出异常
- 注意：get(i)方法不会改变position的值
20201109145822.png
- rewind()方法
- 该方法只能在读模式下使用
- rewind()方法后，会恢复position、limit和capacity的值，变为进行get()前的值
20201109145852.png
- clean()方法
- clean()方法会将缓冲区中的各个属性恢复为最初的状态，position = 0, capacity = limit
- 此时缓冲区的数据依然存在，处于“被遗忘”状态，下次进行写操作时会覆盖这些数据
20201109145905.png
- mark() reset()方法
- mark()方法会将postion的值保存到mark属性中
- reset()方法会将position的值改为mark中保存的值
- compact()方法
- compact会把未读完的数据向前压缩，然后切换到写模式
- 数据前移后，原位置的值并未清零，写时会覆盖之前的值
- 此方法是ByteBuffer的方法，不是Buffer的方法
20210412155726.png
注意：clear只是对position、limit、mark进行重置，而compact在对position进行设置，以及limit、mark进行重置的同时，还涉及到数据在内存中拷贝（会调用arraycopy）。所以compact比clear更耗性能。但compact能保存你未读取的数据，将新数据追加到为读取的数据之后；而clear则不行，若你调用了clear，则未读取的数据就无法再读取到了
2.3 相关方法调用
2.3.1 ByteBuffer调试工具类
- 导入netty依赖
<dependency>
<groupId>io.netty</groupId>
<artifactId>netty-all</artifactId>
<version>4.1.51.Final</version>
</dependency>
- 工具类
import java.nio.ByteBuffer;
import io.netty.util.internal.MathUtil;
import io.netty.util.internal.StringUtil;
import io.netty.util.internal.MathUtil.*;
/**
* @author Panwen Chen
* @date 2021/4/12 15:59
*/
public class ByteBufferUtil {
private static final char[] BYTE2CHAR = new char[256];
private static final char[] HEXDUMP_TABLE = new char[256 * 4];
private static final String[] HEXPADDING = new String[16];
private static final String[] HEXDUMP_ROWPREFIXES = new String[65536 >>> 4];
private static final String[] BYTE2HEX = new String[256];
private static final String[] BYTEPADDING = new String[16];
static {
final char[] DIGITS = "0123456789abcdef".toCharArray();
for (int i = 0; i < 256; i++) {
HEXDUMP_TABLE[i << 1] = DIGITS[i >>> 4 & 0x0F];
HEXDUMP_TABLE[(i << 1) + 1] = DIGITS[i & 0x0F];
}
int i;
// Generate the lookup table for hex dump paddings
for (i = 0; i < HEXPADDING.length; i++) {
int padding = HEXPADDING.length - i;
StringBuilder buf = new StringBuilder(padding * 3);
for (int j = 0; j < padding; j++) {
buf.append(" ");
}
HEXPADDING[i] = buf.toString();
}
// Generate the lookup table for the start-offset header in each row (up to 64KiB).
for (i = 0; i < HEXDUMP_ROWPREFIXES.length; i++) {
StringBuilder buf = new StringBuilder(12);
buf.append(StringUtil.NEWLINE);
buf.append(Long.toHexString(i << 4 & 0xFFFFFFFFL | 0x100000000L));
buf.setCharAt(buf.length() - 9, '|');
buf.append('|');
HEXDUMP_ROWPREFIXES[i] = buf.toString();
}
// Generate the lookup table for byte-to-hex-dump conversion
for (i = 0; i < BYTE2HEX.length; i++) {
BYTE2HEX[i] = ' ' + StringUtil.byteToHexStringPadded(i);
}
// Generate the lookup table for byte dump paddings
for (i = 0; i < BYTEPADDING.length; i++) {
int padding = BYTEPADDING.length - i;
StringBuilder buf = new StringBuilder(padding);
for (int j = 0; j < padding; j++) {
buf.append(' ');
}
BYTEPADDING[i] = buf.toString();
}
// Generate the lookup table for byte-to-char conversion
for (i = 0; i < BYTE2CHAR.length; i++) {
if (i <= 0x1f || i >= 0x7f) {
BYTE2CHAR[i] = '.';
} else {
BYTE2CHAR[i] = (char) i;
}
}
}
/**
* 打印所有内容
* @param buffer
*/
public static void debugAll(ByteBuffer buffer) {
int oldlimit = buffer.limit();
buffer.limit(buffer.capacity());
StringBuilder origin = new StringBuilder(256);
appendPrettyHexDump(origin, buffer, 0, buffer.capacity());
System.out.println("+--------+-------------------- all ------------------------+----------------+");
System.out.printf("position: [%d], limit: [%d]\n", buffer.position(), oldlimit);
System.out.println(origin);
buffer.limit(oldlimit);
}
/**
* 打印可读取内容
* @param buffer
*/
public static void debugRead(ByteBuffer buffer) {
StringBuilder builder = new StringBuilder(256);
appendPrettyHexDump(builder, buffer, buffer.position(), buffer.limit() - buffer.position());
System.out.println("+--------+-------------------- read -----------------------+----------------+");
System.out.printf("position: [%d], limit: [%d]\n", buffer.position(), buffer.limit());
System.out.println(builder);
}
private static void appendPrettyHexDump(StringBuilder dump, ByteBuffer buf, int offset, int length) {
if (MathUtil.isOutOfBounds(offset, length, buf.capacity())) {
throw new IndexOutOfBoundsException(
"expected: " + "0 <= offset(" + offset + ") <= offset + length(" + length
+ ") <= " + "buf.capacity(" + buf.capacity() + ')');
}
if (length == 0) {
return;
}
dump.append(
" +-------------------------------------------------+" +
StringUtil.NEWLINE + " | 0 1 2 3 4 5 6 7 8 9 a b c d e f |" +
StringUtil.NEWLINE + "+--------+-------------------------------------------------+----------------+");
final int startIndex = offset;
final int fullRows = length >>> 4;
final int remainder = length & 0xF;
// Dump the rows which have 16 bytes.
for (int row = 0; row < fullRows; row++) {
int rowStartIndex = (row << 4) + startIndex;
// Per-row prefix.
appendHexDumpRowPrefix(dump, row, rowStartIndex);
// Hex dump
int rowEndIndex = rowStartIndex + 16;
for (int j = rowStartIndex; j < rowEndIndex; j++) {
dump.append(BYTE2HEX[getUnsignedByte(buf, j)]);
}
dump.append(" |");
// ASCII dump
for (int j = rowStartIndex; j < rowEndIndex; j++) {
dump.append(BYTE2CHAR[getUnsignedByte(buf, j)]);
}
dump.append('|');
}
// Dump the last row which has less than 16 bytes.
if (remainder != 0) {
int rowStartIndex = (fullRows << 4) + startIndex;
appendHexDumpRowPrefix(dump, fullRows, rowStartIndex);
// Hex dump
int rowEndIndex = rowStartIndex + remainder;
for (int j = rowStartIndex; j < rowEndIndex; j++) {
dump.append(BYTE2HEX[getUnsignedByte(buf, j)]);
}
dump.append(HEXPADDING[remainder]);
dump.append(" |");
// Ascii dump
for (int j = rowStartIndex; j < rowEndIndex; j++) {
dump.append(BYTE2CHAR[getUnsignedByte(buf, j)]);
}
dump.append(BYTEPADDING[remainder]);
dump.append('|');
}
dump.append(StringUtil.NEWLINE +
"+--------+-------------------------------------------------+----------------+");
}
private static void appendHexDumpRowPrefix(StringBuilder dump, int row, int rowStartIndex) {
if (row < HEXDUMP_ROWPREFIXES.length) {
dump.append(HEXDUMP_ROWPREFIXES[row]);
} else {
dump.append(StringUtil.NEWLINE);
dump.append(Long.toHexString(rowStartIndex & 0xFFFFFFFFL | 0x100000000L));
dump.setCharAt(dump.length() - 9, '|');
dump.append('|');
}
}
public static short getUnsignedByte(ByteBuffer buffer, int index) {
return (short) (buffer.get(index) & 0xFF);
}
}
2.3.2 调用ByteBuffer方法查看内部结构
public class ByteBufferCoreTest {
public static void main(String[] args) {
ByteBuffer buffer = ByteBuffer.allocate(10);
// 向buffer中写入1个字节的数据
buffer.put((byte)97);
ByteBufferUtil.debugAll(buffer);
// 向buffer中写入4个字节的数据
buffer.put(new byte[]{98,99,100,101});
ByteBufferUtil.debugAll(buffer);
// 切换读模式，获取数据
buffer.flip();
ByteBufferUtil.debugAll(buffer);
System.out.println(buffer.get());
System.out.println(buffer.get());
ByteBufferUtil.debugAll(buffer);
// 使用compact切换写模式
buffer.compact();
ByteBufferUtil.debugAll(buffer);
// 再次写入
buffer.put((byte)102);
buffer.put((byte)103);
ByteBufferUtil.debugAll(buffer);
}
}
- result
+--------+-------------------- all ------------------------+----------------+
position: [1], limit: [10]
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 61 00 00 00 00 00 00 00 00 00 |a......... |
+--------+-------------------------------------------------+----------------+
+--------+-------------------- all ------------------------+----------------+
position: [5], limit: [10]
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 61 62 63 64 65 00 00 00 00 00 |abcde..... |
+--------+-------------------------------------------------+----------------+
+--------+-------------------- all ------------------------+----------------+
position: [0], limit: [5]
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 61 62 63 64 65 00 00 00 00 00 |abcde..... |
+--------+-------------------------------------------------+----------------+
97
98
+--------+-------------------- all ------------------------+----------------+
position: [2], limit: [5]
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 61 62 63 64 65 00 00 00 00 00 |abcde..... |
+--------+-------------------------------------------------+----------------+
+--------+-------------------- all ------------------------+----------------+
position: [3], limit: [10]
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 63 64 65 64 65 00 00 00 00 00 |cdede..... |
+--------+-------------------------------------------------+----------------+
+--------+-------------------- all ------------------------+----------------+
position: [5], limit: [10]
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 63 64 65 66 67 00 00 00 00 00 |cdefg..... |
+--------+-------------------------------------------------+----------------+
2.4 字符串和ByteBuffer转换
- 方法一，通过StandardCharsets的encode和decode方法
public class Translate {
public static void main(String[] args) {
String str1 = "Hello World";
String str2 = "";
// 通过StandardCharsets的encode方法获得ByteBuffer
// 此时获得的ByteBuffer为读模式，无需通过flip切换模式
ByteBuffer buffer = StandardCharsets.UTF_8.encode(str1);
ByteBufferUtil.debugAll(buffer);
//如果差人一次get()则最后打印的字符串变为 ello World，原因是position目前的位置变为1，导致读取时忽略了position=0位置的数据
//System.out.println(buffer.get());
// 将缓冲区中的数据转化为字符串
// 通过StandardCharsets解码，获得CharBuffer，再通过toString获得字符串
str2 = StandardCharsets.UTF_8.decode(buffer).toString();
System.out.println(str2);
ByteBufferUtil.debugAll(buffer);
}
}
- result
+--------+-------------------- all ------------------------+----------------+
position: [0], limit: [11]
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 48 65 6c 6c 6f 20 57 6f 72 6c 64 00 |Hello World. |
+--------+-------------------------------------------------+----------------+
Hello World
+--------+-------------------- all ------------------------+----------------+
position: [11], limit: [11]
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 48 65 6c 6c 6f 20 57 6f 72 6c 64 00 |Hello World. |
+--------+-------------------------------------------------+----------------+
- 方法二，将字节数组传给ByteBuffer的wrap()方法，通过该方法获得ByteBuffer。同样无需调用flip方法切换为读模式
public class Translate {
public static void main(String[] args) {
String str1 = "Hello World";
String str2 = "";
ByteBuffer buffer = ByteBuffer.wrap(str1.getBytes());
ByteBufferUtil.debugAll(buffer);
str2 = StandardCharsets.UTF_8.decode(buffer).toString();
System.out.println(str2);
ByteBufferUtil.debugAll(buffer);
}
}
- result
+--------+-------------------- all ------------------------+----------------+
position: [0], limit: [11]
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 48 65 6c 6c 6f 20 57 6f 72 6c 64 |Hello World |
+--------+-------------------------------------------------+----------------+
Hello World
+--------+-------------------- all ------------------------+----------------+
position: [11], limit: [11]
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 48 65 6c 6c 6f 20 57 6f 72 6c 64 |Hello World |
+--------+-------------------------------------------------+----------------+
2.5 粘包与半包
2.5.1 现象
网络上有多条数据发送给服务端，数据之间使用 \n 进行分隔
但由于某种原因这些数据在接收时，被进行了重新组合，例如原始数据有3条为
- Hello,world\n
- I’m Nyima\n
- How are you?\n
变成了下面的两个 byteBuffer (粘包，半包)
- Hello,world\nI’m Nyima\nHo
- w are you?\n
2.5.2 解决办法
public class ByteBufferPackageTest {
public static void main(String[] args) {
ByteBuffer buffer = ByteBuffer.allocate(32);
// 模拟粘包+半包
buffer.put("Hello,world\nI'm Nyima\nHo".getBytes());
// 调用split函数处理
split(buffer);
buffer.put("w are you?\n".getBytes());
split(buffer);
}
public static void split(ByteBuffer buffer){
// 切换为读模式
buffer.flip();
for (int i = 0; i < buffer.limit(); i++) {
// 遍历寻找分隔符
// get(i)不会移动position
if (buffer.get(i) == '\n'){
// 缓冲区长度
int length = i + 1 - buffer.position();
ByteBuffer target = ByteBuffer.allocate(length);
// 将前面的内容写入target缓冲区
for (int j = 0; j < length; j++) {
// 将buffer中的数据写入target中
target.put(buffer.get());
}
ByteBufferUtil.debugAll(target);
}
}
// 切换为写模式，但是缓冲区可能未读完，这里需要使用compact
buffer.compact();
}
}
- result
+--------+-------------------- all ------------------------+----------------+
position: [12], limit: [12]
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 48 65 6c 6c 6f 2c 77 6f 72 6c 64 0a |Hello,world. |
+--------+-------------------------------------------------+----------------+
+--------+-------------------- all ------------------------+----------------+
position: [10], limit: [10]
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 49 27 6d 20 4e 79 69 6d 61 0a |I'm Nyima. |
+--------+-------------------------------------------------+----------------+
+--------+-------------------- all ------------------------+----------------+
position: [13], limit: [13]
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 48 6f 77 20 61 72 65 20 79 6f 75 3f 0a |How are you?. |
+--------+-------------------------------------------------+----------------+
二 文件编程
1 FileChannel
FileChannel只能在阻塞模式下工作，所以无法搭配Selector
1.1 获取channel
不能直接打开 FileChannel，必须通过 FileInputStream、FileOutputStream 或者 RandomAccessFile 来获取 FileChannel，它们都有 getChannel 方法
- 通过 FileInputStream 获取的 channel 只能读
- 通过 FileOutputStream 获取的 channel 只能写
- 通过 RandomAccessFile 是否能读写根据构造 RandomAccessFile 时的读写模式决定
1.2 读取channel
通过 FileInputStream 获取channel，通过read方法将数据写入到ByteBuffer中，read方法的返回值表示读到了多少字节，若读到了文件末尾则返回-1
int readBytes = channel.read(buffer);
根据返回值判断是否读取完毕
while(channel.read(buffer) > 0) {
// 进行对应操作
...
}
1.3 写入channel
因为channel也是有大小的，所以 write 方法并不能保证一次将 buffer 中的内容全部写入 channel。需要按照以下规则进行写入
// 通过hasRemaining()方法查看缓冲区中是否还有数据未写入到通道中
while(buffer.hasRemaining()) {
channel.write(buffer);
}
1.4 关闭channel
通道需要close，一般情况通过try-with-resource进行关闭，最好使用以下方法获取stream以及channel，避免某些原因使得资源未被关闭
public class TestChannel {
public static void main(String[] args) throws IOException {
try (FileInputStream fis = new FileInputStream("stu.txt");
FileOutputStream fos = new FileOutputStream("student.txt");
FileChannel inputChannel = fis.getChannel();
FileChannel outputChannel = fos.getChannel()) {
// 执行对应操作
...
}
}
}
2 两个channel传输数据
使用transferTo方法可以快速、高效地将一个channel中的数据传输到另一个channel中，但一次只能传输2G的内容，transferTo底层使用了零拷贝技术
public class TransferToTest {
public static void main(String[] args) {
try (FileChannel inputChannel = new FileInputStream("data.txt").getChannel();
FileChannel outputChannel = new FileOutputStream("data2.txt").getChannel()) {
// 参数：inputChannel的起始位置，传输数据的大小，目的channel
// 返回值为传输的数据的字节数
// transferTo一次只能传输2G的数据
inputChannel.transferTo(0,inputChannel.size(),outputChannel);
} catch (IOException e) {
e.printStackTrace();
}
}
}
当传输的文件大于2G时，需要使用以下方法进行多次传输
public class TransferToTest {
public static void main(String[] args) {
try (FileChannel inputChannel = new FileInputStream("data.txt").getChannel();
FileChannel outputChannel = new FileOutputStream("data2.txt").getChannel()) {
long size = inputChannel.size();
long capacity = inputChannel.size();
// 分多次传输
while (capacity > 0){
// transferTo返回值为传输了的字节数
capacity -= inputChannel.transferTo(size-capacity,capacity,outputChannel);
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
3 Path和Paths
- Path 用来表示文件路径
- Paths 是工具类，用来获取 Path 实例
Path source = Paths.get("1.txt"); // 相对路径 不带盘符 使用 user.dir 环境变量来定位 1.txt
Path source = Paths.get("d:\\1.txt"); // 绝对路径代表了 d:\1.txt 反斜杠需要转义
Path source = Paths.get("d:/1.txt"); // 绝对路径同样代表了 d:\1.txt
Path projects = Paths.get("d:\\data", "projects"); // 代表了 d:\data\projects
-
.代表了当前路径 -
..代表了上一级路径
4 Files
4.1 查找
Path path = Paths.get("helloword/data.txt");
System.out.println(Files.exists(path)); //检查文件是否存在
4.2 创建
- 创建一级目录
- 如果目录已存在，会抛异常 FileAlreadyExistsException
- 不能一次创建多级目录，否则会抛异常 NoSuchFileException
Path path = Paths.get("helloword/d1");
Files.createDirectory(path);
- 创建多级目录
Path path = Paths.get("helloword/d1/d2");
Files.createDirectories(path);
4.3 拷贝和移动
- 拷贝文件
- 如果文件已存在，会抛异常 FileAlreadyExistsException
Path source = Paths.get("helloword/data.txt");
Path target = Paths.get("helloword/target.txt");
Files.copy(source, target);
//如果希望用 source 覆盖掉 target，需要用 StandardCopyOption 来控制
//Files.copy(source, target, StandardCopyOption.REPLACE_EXISTING);
- 移动文件
Path source = Paths.get("helloword/data.txt");
Path target = Paths.get("helloword/data.txt");
//StandardCopyOption.ATOMIC_MOVE 保证文件移动的原子性
Files.move(source, target, StandardCopyOption.ATOMIC_MOVE);
4.4 删除
- 删除文件
- 如果文件不存在，会抛异常 NoSuchFileException
Path target = Paths.get("helloword/target.txt");
Files.delete(target);
- 删除目录
- 如果目录还有内容，会抛异常 DirectoryNotEmptyException
Path target = Paths.get("helloword/d1");
Files.delete(target);
4.5 遍历文件
可以使用Files工具类中的walkFileTree(Path, FileVisitor)方法，其中需要传入两个参数
Path：文件起始路径
-
FileVisitor：文件访问器，
使用访问者模式
-
接口的实现类
SimpleFileVisitor
有四个方法
- preVisitDirectory：访问目录前的操作
- visitFile：访问文件的操作
- visitFileFailed：访问文件失败时的操作
- postVisitDirectory：访问目录后的操作
-
public class WalkFileTreeTest {
public static void main(String[] args) throws IOException {
Path path = Paths.get("/Users/yorick/Documents/leisure");
// 文件目录数目
AtomicInteger dirCount = new AtomicInteger();
// 文件数目
AtomicInteger fileCount = new AtomicInteger();
Files.walkFileTree(path,new SimpleFileVisitor<Path>(){
@Override
public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) throws IOException {
System.out.println("===>"+dir);
// 增加文件目录数
dirCount.incrementAndGet();
return super.preVisitDirectory(dir, attrs);
}
@Override
public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
System.out.println(file);
// 增加文件数
fileCount.incrementAndGet();
return super.visitFile(file, attrs);
}
});
// 打印数目
System.out.println(dirCount);
System.out.println(fileCount);
}
}
