[Utils - JDK] 2 Files

This class consists exclusively of static methods that operate on files, directories, or other types of files...

Posted by Mr.Vincent on 2020-09-13
Estimated Reading Time 19 Minutes
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Viewed Times

概述

JDK1.7引入了新的IO操作类。java.nio 包下定义了一些操作文件和文件系统的接口和类。java.nio.file.Files 类具有对文件、目录和其他类型的文件进行操作的静态实用程序方法。在这篇文章中,我们将学习 java.nio 文件 API。Files 类在 java.nio.file 包下。这篇文章将介绍有关文件操作的 NIO Files 类。

Java NIO Paths

java.nio.file 包下有一个 Path 类,这个类用于来表示文件路径和文件。在 JDK 1.7 中 Path 类取代了 File 类。NIO Files 类中的 API 就通过 Path 类来工作。

构造 Path 的方法(Java 8)

  • get(String first, String... more):将路径字符串或联接后形成路径字符串的字符串序列转换为路径。

  • Path get(URI uri):将给定的URI转换为路径对象。

例:

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@Test
public void path() {
Path path = Paths.get("/Users/vincent/IDEA_Project/my_project/IO/sample-file.txt");
System.out.println(path.getFileName());

Path path2 = Paths.get("/Users", "/vincent", "/IDEA_Project", "/my_project/IO/sample-file.txt");
System.out.println(path2.getFileName());
}

或者另一种创建路径的方法是通过创建一个 URI。

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Path path3 = Paths.get(URI.create("file:///Users/vincent/IDEA_Project/my_project/IO/sample-file.txt"));
System.out.println(path3.getFileName());

从 Java 11 开始,Paths.get() 不建议使用。取而代之的,推荐用 Path接口中的 static of() 方法来创建。它和 Paths.get() 方法没有区别。

例:

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Path path = Path.of("/Users/vincent/IDEA_Project/my_project/IO/sample-file.txt");
Path path = Path.of("/Users", "/vincent", "/IDEA_Project", "/my_project/IO/sample-file.txt");
Path path = Path.of(URI.create("file:///Users/vincent/IDEA_Project/my_project/IO/sample-file.txt"));

Path 部分方法

  • toFile():获取文件。
  • getFileName():获取文件名。
  • toUri():获取 URI(例:file:///Users/vincent/IDEA_Project/my_project/IO/sample-file.txt)。
  • getParent():获取父路径。
  • getRoot():获取根路径。
  • toString():该路径的字符串形式。
  • isAbsolute():是否是绝对路径。

例:

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@Test
public void path(){
Path path = Paths.get("/Users/vincent/IDEA_Project/my_project/IO/sample-file.txt");

File file = path.toFile();
System.out.println(file);

Path fileName = path.getFileName();
System.out.println(fileName);

URI uri = path.toUri();
System.out.println(uri);

Path parent = path.getParent();
System.out.println(parent);

Path root = path.getRoot();
System.out.println(root);

boolean absolute = path.isAbsolute();
System.out.println(absolute);
}

Java NIO Files

常用方法

  • exists(Path path, LinkOption... options):是否存在。
  • notExists(Path path, LinkOption... options):是否不存在。
  • isDirectory(Path path, LinkOption... options):是否是目录。
  • isSymbolicLink(Path path):是否是象征链接。
  • isWritable(Path path):是否可写。
  • isExecutable(Path path):是否可执行。
  • isReadable(Path path):是否可读。
  • isHidden(Path path):是否是隐藏。
  • getPosixFilePermissions(Path path, LinkOption... options):获取具体的权限。
  • getOwner(Path path, LinkOption... options)
  • getLastModifiedTime(Path path, LinkOption... options):获取最后修改时间。
  • size(Path path):获取大小。
  • newInputStream(Path path, OpenOption... options):返回输入流。
  • newOutputStream(Path path, OpenOption... options):返回输出流。

例:

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@Test
public void files() throws IOException {
/**
* exists(Path path, LinkOption... options):是否存在。
* notExists(Path path, LinkOption... options):是否不存在。
* isDirectory(Path path, LinkOption... options):是否是目录。
* isSymbolicLink(Path path):是否是象征链接。
* isWritable(Path path):是否可写。
* isExecutable(Path path):是否可执行。
* isReadable(Path path):是否可读。
* isHidden(Path path):是否是隐藏。
* getPosixFilePermissions(Path path, LinkOption... options):获取具体的权限。
* getOwner(Path path, LinkOption... options):获取所属者。
* getLastModifiedTime(Path path, LinkOption... options):获取最后修改时间。
* size(Path path):获取大小。
*/
Path newFilePath2 = Paths.get("/Users/vincent/IDEA_Project/my_project/IO/new-file2.txt");

boolean exists = Files.exists(newFilePath2);
System.out.println("exists::" + exists);

boolean notExists = Files.notExists(newFilePath2);
System.out.println("notExists:" + notExists);

boolean directory = Files.isDirectory(newFilePath2);
System.out.println("directory:" + directory);

boolean symbolicLink = Files.isSymbolicLink(newFilePath2);
System.out.println("symbolicLink:" + symbolicLink);

boolean writable = Files.isWritable(newFilePath2);
System.out.println("writable:" + symbolicLink);

boolean executable = Files.isExecutable(newFilePath2);
System.out.println("executable:" + symbolicLink);

boolean readable = Files.isReadable(newFilePath2);
System.out.println("readable:" + symbolicLink);

boolean hidden = Files.isHidden(newFilePath2);
System.out.println("hidden:" + symbolicLink);

Set<PosixFilePermission> posixFilePermissions = Files.getPosixFilePermissions(newFilePath2);
posixFilePermissions.forEach(System.out::println);

UserPrincipal owner = Files.getOwner(newFilePath2);
System.out.println("owner:" + owner);

FileTime lastModifiedTime = Files.getLastModifiedTime(newFilePath2);
System.out.println("lastModifiedTime:" + lastModifiedTime);

long size = Files.size(newFilePath2);
System.out.println("size:" + size);
}

显示结果:

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exists::true
notExists:false
directory:false
symbolicLink:false
writable:false
executable:false
readable:false
hidden:false
OWNER_WRITE
owner:vincent
lastModifiedTime:2020-09-13T16:40:27Z
size:0

readAttributes

readAttributes:读取文件的全部属性,作为一个批次操作。

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readAttributes(Path path, Class<A> type, LinkOption... options)
readAttributes(Path path, String attributes, LinkOption... options)

例:

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@Test
public void readAttributes() throws IOException {
/**
* readAttributes:读取文件的全部属性,作为一个批次操作。
*
* readAttributes(Path path, Class<A> type, LinkOption... options)
* readAttributes(Path path, String attributes, LinkOption... options)
*/
Path pathFile = Paths.get("/Users/vincent/IDEA_Project/my_project/IO/new-file2.txt");
PosixFileAttributes attrs = Files.readAttributes(pathFile, PosixFileAttributes.class);// 读取文件的权限
Set<PosixFilePermission> posixPermissions = attrs.permissions();
posixPermissions.clear();
System.out.format("%s %s%n", attrs.owner().getName(), PosixFilePermissions.toString(posixPermissions));
Files.setPosixFilePermissions(pathFile, posixPermissions);

posixPermissions.add(PosixFilePermission.OWNER_READ);
posixPermissions.add(PosixFilePermission.GROUP_READ);
posixPermissions.add(PosixFilePermission.OTHERS_READ);
posixPermissions.add(PosixFilePermission.OWNER_WRITE);
// 设置文件的权限
Files.setPosixFilePermissions(pathFile, posixPermissions);
System.out.format("%s %s%n", attrs.owner().getName(), PosixFilePermissions.toString(attrs.permissions()));
}

createFilecreateDirectory

createFile:创建一个新的空的文件,如果存在创建失败(抛 FileAlreadyExistsException)。

createDirectory:创建一个新的目录,如果存在创建失败(抛 FileAlreadyExistsException)。

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createDirectories(Path dir, FileAttribute<?>... attrs)
createDirectory(Path dir, FileAttribute<?>... attrs)
createFile(Path path, FileAttribute<?>... attrs)

例:

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@Test
public void createFileAndDirectory() throws IOException {
/**
* createFile:创建一个新的空的文件,如果存在创建失败(抛 FileAlreadyExistsException)。
* createDirectory:创建一个新的目录,如果存在创建失败(抛 FileAlreadyExistsException)。
*
* createDirectories(Path dir, FileAttribute<?>... attrs)
* createDirectory(Path dir, FileAttribute<?>... attrs)
* createFile(Path path, FileAttribute<?>... attrs)
*/
Path newFilePath = Paths.get("/Users/vincent/IDEA_Project/my_project/IO/new-file.txt");
Files.createFile(newFilePath);

//设置了权限,只能写的权限。(--w------- 1 vincent staff 0 Sep 14 00:40 new-file2.txt)
Path newFilePath2 = Paths.get("/Users/vincent/IDEA_Project/my_project/IO/new-file2.txt");
FileAttribute<Set<PosixFilePermission>> fileAttributes = PosixFilePermissions
.asFileAttribute(Sets.newHashSet(PosixFilePermission.OWNER_WRITE));
Files.createFile(newFilePath2, fileAttributes);

//Files.createDirectory():只是创建目录,如果它的上级目录不存在就会报错。
Path newDirectoryPath = Paths.get("/Users/vincent/IDEA_Project/my_project/IO/newDir1");
Files.createDirectory(newDirectoryPath);

//Files.createDirectories():会首先创建所有不存在的父目录来创建目录。
Path newDirectoriesPath = Paths.get("/Users/vincent/IDEA_Project/my_project/IO/newDir2/newDir3");
Files.createDirectories(newDirectoriesPath);
}

createTempFilecreateTempDirectory

createTempFile:生成临时文件,支持前缀和后缀命名。

createTempDirectory:生成临时目录,支持前缀命名。

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Path directoryPath = Paths.get("/Users/JavaDeveloperCentral/data");
Path tmpDirPath = Files.createTempDirectory(directoryPath, "");
System.out.println(tmpDirPath);
tmpDirPath.toFile().deleteOnExit();

Path filePath1 = Paths.get(tmpDirPath.toString() + "/file1");
filePath1.toFile().deleteOnExit();
Files.write(filePath1, List.of("something"));

Path filePath2 = Paths.get(tmpDirPath.toString() + "/file2");
filePath2.toFile().deleteOnExit();
Files.write(filePath2, List.of("something"));
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createTempFile(Path dir, String prefix, String suffix, FileAttribute<?>... attrs)
createTempFile(String prefix, String suffix, FileAttribute<?>... attrs)
createTempDirectory(Path dir, String prefix, FileAttribute<?>... attrs)
createTempDirectory(String prefix, FileAttribute<?>... attrs)

例:

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@Test
public void createTempFileAndDirectory() throws IOException {
/**
* createTempFile:生成临时文件,支持前缀和后缀命名。
* createTempDirectory:生成临时目录,支持前缀命名。
*
* createTempFile(Path dir, String prefix, String suffix, FileAttribute<?>... attrs)
* createTempFile(String prefix, String suffix, FileAttribute<?>... attrs)
* createTempDirectory(Path dir, String prefix, FileAttribute<?>... attrs)
* createTempDirectory(String prefix, FileAttribute<?>... attrs)
*/
Path path = Paths.get("/Users/vincent/IDEA_Project/my_project/IO/");
Path tempFile = Files.createTempFile(path, "prefix", "suffix.txt");
System.out.println(tempFile);

//不指定目录,会在系统默认目录下生成。
Path tempFile2 = Files.createTempFile("prefix", "suffix.txt");
System.out.println(tempFile2);

Path tempDirectory = Files.createTempDirectory(path, "prefix");
System.out.println(tempDirectory);

Path tempDirectory2 = Files.createTempDirectory("prefix");
System.out.println(tempDirectory2);
}

readAllBytesreadAllLinesreadStringlineslist

readAllBytes:读取文件,返回字节。

readAllLines:读取文件的所以行,返回 List<String>

readString:读取文件,返回字符串。(Java 11)

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//This method was added in Java 11
String data = Files.readString(filePath);
System.out.println(data);

data = Files.readString(filePath, StandardCharsets.UTF_8);
System.out.println(data);

lines:从文件中读取所有行作为 Stream 。

list:返回一个懒惰的填充 Stream ,其元素是 Stream 中的条目。

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readAllBytes(Path path)
readAllLines(Path path)
readAllLines(Path path, Charset cs)
readString(Path path)
readString(Path path, Charset cs)
lines(Path path)
lines(Path path, Charset cs)
list(Path dir)

例:

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@Test
public void readXxx() throws IOException {
/**
* readAllBytes:读取文件,返回字节。
* readAllLines:读取文件的所以行,返回 List<String>。
* readString:读取文件,返回字符串。(Java 11)
* lines:从文件中读取所有行作为 Stream 。
* list:返回一个懒惰的填充 Stream ,其元素是 Stream 中的条目。
*
* readAllBytes(Path path)
* readAllLines(Path path)
* readAllLines(Path path, Charset cs)
* readString(Path path)(Java 11)
* readString(Path path, Charset cs)(Java 11)
* lines(Path path)
* lines(Path path, Charset cs)
* list(Path dir)
*/
Path filePath = Paths.get("/Users/vincent/IDEA_Project/my_project/IO/sample-file.txt");
byte[] bytes = Files.readAllBytes(filePath);
System.out.println(new String(bytes));
System.out.println();

List<String> readAllLines = Files.readAllLines(filePath, StandardCharsets.UTF_8);
readAllLines.forEach(System.out::println);
System.out.println();

try (Stream<String> lines = Files.lines(filePath)) {
lines.forEach(System.out::println);
}
System.out.println();

Path directoryPath = Paths.get("/Users/vincent/IDEA_Project/my_project/IO");
try (Stream<Path> list = Files.list(directoryPath)) {
list.forEach(System.out::println);
}
}

显示结果:

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1-Will-90
2-James-87
3-Kyle-67

1-Will-90
2-James-87
3-Kyle-67

1-Will-90
2-James-87
3-Kyle-67

/Users/vincent/IDEA_Project/my_project/IO/copyFile.png
/Users/vincent/IDEA_Project/my_project/IO/new-file2.txt
/Users/vincent/IDEA_Project/my_project/IO/sample-output-file.txt
/Users/vincent/IDEA_Project/my_project/IO/IO.iml
/Users/vincent/IDEA_Project/my_project/IO/reader.txt
/Users/vincent/IDEA_Project/my_project/IO/touch
/Users/vincent/IDEA_Project/my_project/IO/target
/Users/vincent/IDEA_Project/my_project/IO/io.png
/Users/vincent/IDEA_Project/my_project/IO/pom.xml
/Users/vincent/IDEA_Project/my_project/IO/writer.txt
/Users/vincent/IDEA_Project/my_project/IO/readerAndWriter.txt
/Users/vincent/IDEA_Project/my_project/IO/touch.txt
/Users/vincent/IDEA_Project/my_project/IO/new-file.txt
/Users/vincent/IDEA_Project/my_project/IO/outputStreamReader.txt
/Users/vincent/IDEA_Project/my_project/IO/inputStreamReader.txt
/Users/vincent/IDEA_Project/my_project/IO/a.txt
/Users/vincent/IDEA_Project/my_project/IO/.gitignore
/Users/vincent/IDEA_Project/my_project/IO/write.txt
/Users/vincent/IDEA_Project/my_project/IO/sample-file.txt
/Users/vincent/IDEA_Project/my_project/IO/io3.png
/Users/vincent/IDEA_Project/my_project/IO/io2.png
/Users/vincent/IDEA_Project/my_project/IO/inputStream.txt
/Users/vincent/IDEA_Project/my_project/IO/fileutils
/Users/vincent/IDEA_Project/my_project/IO/.git
/Users/vincent/IDEA_Project/my_project/IO/copyFile2.png
/Users/vincent/IDEA_Project/my_project/IO/.idea
/Users/vincent/IDEA_Project/my_project/IO/src

writewriteString

write:将内容写入文件。

writeString:将字符写入文件。(Java 11)

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//This method was added in Java 11
//File exists - Append to it
Files.writeString(filePath, data, StandardOpenOption.WRITE, StandardOpenOption.APPEND);

//File exists - Truncate existing data
Files.writeString(filePath, data, StandardOpenOption.WRITE, StandardOpenOption.TRUNCATE_EXISTING);

//File does not exist, create a new one and write
Files.writeString(filePath, data, StandardOpenOption.CREATE_NEW);

//Create file if it does not exist and Append to it
Files.writeString(filePath, data, StandardOpenOption.CREATE, StandardOpenOption.APPEND);

//Create file if it does not exist - Truncate existing data
Files.writeString(filePath, data, StandardOpenOption.CREATE, StandardOpenOption.TRUNCATE_EXISTING);
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write(Path path, byte[] bytes, OpenOption... options)
write(Path path, Iterable<? extends CharSequence> lines, Charset cs, OpenOption... options)
write(Path path, Iterable<? extends CharSequence> lines, OpenOption... options)
writeString(Path path, CharSequence csq, Charset cs, OpenOption... options) (Java 11
writeString(Path path, CharSequence csq, OpenOption... options)(Java 11

例:

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@Test
public void writeXxx() throws IOException {
/**
* write:将内容写入文件。
* writeString:将字符写入文件。(Java 11)
*
* write(Path path, byte[] bytes, OpenOption... options)
* write(Path path, Iterable<? extends CharSequence> lines, Charset cs, OpenOption... options)
* write(Path path, Iterable<? extends CharSequence> lines, OpenOption... options)
* writeString(Path path, CharSequence csq, Charset cs, OpenOption... options) (Java 11)
* writeString(Path path, CharSequence csq, OpenOption... options)(Java 11)
*/
Path filePath = Paths.get("/Users/vincent/IDEA_Project/my_project/IO/sample-file.txt");
Path filePath2 = Paths.get("/Users/vincent/IDEA_Project/my_project/IO/sample-output-file.txt");
Path write = Files.write(filePath2, Files.readAllBytes(filePath));

//StandardOpenOption.APPEND:追加在原文件内容后。
Path write2 = Files.write(filePath2, Lists.newArrayList("a", "b", "c"), StandardCharsets.UTF_8, StandardOpenOption.APPEND);
}

copy

copy:复制文件或目录。

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copy(InputStream in, Path target, CopyOption... options)	
copy(Path source, OutputStream out)
copy(Path source, Path target, CopyOption... options)

例:

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    @Test
public void copy() throws IOException {
/**
* copy:复制文件或目录。
*
* copy(InputStream in, Path target, CopyOption... options)
* copy(Path source, OutputStream out)
* copy(Path source, Path target, CopyOption... options)
*/
Path sourceFilePath = Paths.get("/Users/vincent/IDEA_Project/my_project/IO/source.txt");
Path destinationFilePath = Paths.get("/Users/vincent/IDEA_Project/my_project/IO/destination.txt");

//StandardCopyOption.REPLACE_EXISTING:如果存在,则替换。
Files.copy(sourceFilePath, destinationFilePath, StandardCopyOption.REPLACE_EXISTING);

// Files.copy(sourceFilePath, new FileOutputStream(destinationFilePath.toFile()));
Files.copy(sourceFilePath, Files.newOutputStream(destinationFilePath, StandardOpenOption.WRITE));

// Files.copy(IOUtils.toInputStream("Vincent is so handsome!!!", StandardCharsets.UTF_8), destinationFilePath, StandardCopyOption.REPLACE_EXISTING);
Files.copy(Files.newInputStream(sourceFilePath), destinationFilePath, StandardCopyOption.REPLACE_EXISTING);
}

movedeletedeleteIfExists

move:移动或重命名文件到目标文件;移动或重命名目录(注:被移动或重命名的目录必须为空目录)。

delete:删除文件。

deleteIfExists:如果存在删除文件。

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move(Path source, Path target, CopyOption... options)
delete(Path path)
deleteIfExists(Path path)

例:

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@Test
public void moveAndDelete() throws IOException {
/**
* move:移动或重命名文件到目标文件;移动或重命名目录(注:被移动或重命名的目录必须为空目录)。
* delete:删除文件。
* deleteIfExists:如果存在删除文件。
*
* move(Path source, Path target, CopyOption... options)
* delete(Path path)
* deleteIfExists(Path path)
*/
Path sourceFilePath = Paths.get("/Users/vincent/IDEA_Project/my_project/IO/source.txt");
Path destinationFilePath = Paths.get("/Users/vincent/IDEA_Project/my_project/IO/new_source.txt");
Files.move(sourceFilePath, destinationFilePath, StandardCopyOption.REPLACE_EXISTING);

Path path1 = Paths.get("/Users/vincent/IDEA_Project/my_project/IO/newData");
Path path2 = Paths.get("/Users/vincent/IDEA_Project/my_project/IO/dir1/dir2");
//Works only if on the same filestore - else use walkFileTree
Files.move(path1, path2);

Path filePathToDelete = Paths.get("/Users/vincent/IDEA_Project/my_project/IO/a.txt");
Files.delete(filePathToDelete);

//deletes only if it exists
Files.deleteIfExists(filePathToDelete);
}

newDirectoryStream

newDirectoryStream:遍历当前目录(仅当前目录)下的所以条目(但不做递归遍历)。

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newDirectoryStream(Path dir)
newDirectoryStream(Path dir, DirectoryStream.Filter<? super Path> filter)
newDirectoryStream(Path dir, String glob)

例:

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@Test
public void newDirectoryStream() throws IOException {
/**
* newDirectoryStream:遍历当前目录(仅当前目录)下的所以条目(但不做递归遍历)。
* 这里有个目录,目录结构如下:
* |-- data
* |-- file1.txt
* |-- file2.txt
* |-- SomeClass.java
* |-- dir1
* |-- dir2
* |-- file1InDir2.txt
* |-- file3.txt
*
* 调用 newDirectoryStream(Path dir) 后,输出打印:
* file1.txt
* file2.txt
* SomeClass.java
* dir1
* file3.txt
*
* newDirectoryStream(Path dir)
* newDirectoryStream(Path dir, DirectoryStream.Filter<? super Path> filter)
* newDirectoryStream(Path dir, String glob)
*/
Path directoryPath = Paths.get("/Users/vincent/IDEA_Project/my_project/IO/fileutils");
try (DirectoryStream<Path> directoryStream = Files.newDirectoryStream(directoryPath)) {
directoryStream.forEach(System.out::println);
}
System.out.println();

try (DirectoryStream<Path> directoryStream = Files.newDirectoryStream(directoryPath, path -> path.toFile().isFile())) {
directoryStream.forEach(System.out::println);
}
System.out.println();

try (DirectoryStream<Path> directoryStream = Files.newDirectoryStream(directoryPath, "*.txt")) {
directoryStream.forEach(System.out::println);
}
}

显示结果:

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file1.txt
file2.txt
SomeClass.java
dir1
file3.txt

file1.txt
file2.txt
SomeClass.java
file3.txt

file1.txt
file2.txt
file3.txt

walkwalkFileTree

walk:遍历整个文件目录(递归)。

walkFileTree:遍历整个文件目录(递归)。

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walk(Path start, FileVisitOption... options)
walk(Path start, int maxDepth, FileVisitOption... options)
walkFileTree(Path start, FileVisitor<? super Path> visitor)
walkFileTree(Path start, Set<FileVisitOption> options, int maxDepth, FileVisitor<? super Path> visitor)

例:

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@Test
public void walkAndWalkFileTree() throws IOException {
/**
* walk:遍历整个文件目录(递归)。
* walkFileTree:遍历整个文件目录(递归)。
*
* walk(Path start, FileVisitOption... options)
* walk(Path start, int maxDepth, FileVisitOption... options)
* walkFileTree(Path start, FileVisitor<? super Path> visitor)
* walkFileTree(Path start, Set<FileVisitOption> options, int maxDepth, FileVisitor<? super Path> visitor)
*/
Path directoryPath = Paths.get("/Users/vincent/IDEA_Project/my_project/IO/fileutils");
try (Stream<Path> walk = Files.walk(directoryPath, 1)) {
walk.forEach(System.out::println);
}
System.out.println();


/**
* walkFileTree(Path start, Set<FileVisitOption> options, int maxDepth, FileVisitor<? super Path> visitor):
* 参数:
* 1. java.nio.file.Path start:遍历的起始路径。
* 2. Set<java.nio.file.FileVisitOption> options:遍历选项。
* 3. int maxDepth:遍历深度。
* 4. java.nio.file.FileVisitor<? super Path> visitor:遍历过程中的行为控制器。
*
* FileVisitor<Path>:
* 1. preVisitDirectory:访问一个目录,在进入之前调用。
* 2. postVisitDirectory:一个目录的所有节点都被访问后调用。遍历时跳过同级目录或有错误发生,Exception 会传递给这个方法。
* 3. visitFile:文件被访问时被调用。该文件的文件属性被传递给这个方法。
* 4. visitFileFailed:当文件不能被访问时,此方法被调用。Exception 被传递给这个方法。
* FileVisitResult:
* 1. CONTINUE:继续遍历。
* 2. SKIP_SIBLINGS:继续遍历,但忽略当前节点的所有兄弟节点直接返回上一层继续遍历。
* 3. SKIP_SUBTREE:继续遍历,但是忽略子目录,但是子文件还是会访问。
* 4. TERMINATE:终止遍历。
*
*/
Files.walkFileTree(directoryPath, new MySimpleFileVisitorImpl());
System.out.println();

Files.walkFileTree(directoryPath, Sets.newHashSet(FileVisitOption.FOLLOW_LINKS), 1, new SimpleFileVisitor<Path>() {
@Override
public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
System.out.println("visitFile " + file);
return super.visitFile(file, attrs);
}
});

}

public class MySimpleFileVisitorImpl implements FileVisitor<Path> {
@Override
public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) throws IOException {
System.out.println("preVisitDirectory " + dir);
return FileVisitResult.CONTINUE;
}

@Override
public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
System.out.println("visitFile " + file);
return FileVisitResult.CONTINUE;
}

@Override
public FileVisitResult visitFileFailed(Path file, IOException exc) throws IOException {
System.out.println("visitFileFailed " + file);
return FileVisitResult.CONTINUE;
}

@Override
public FileVisitResult postVisitDirectory(Path dir, IOException exc) throws IOException {
System.out.println("postVisitDirectory " + dir);
return FileVisitResult.CONTINUE;
}
}

显示结果:

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/Users/vincent/IDEA_Project/my_project/IO/fileutils
/Users/vincent/IDEA_Project/my_project/IO/fileutils/abc
/Users/vincent/IDEA_Project/my_project/IO/fileutils/io.png
/Users/vincent/IDEA_Project/my_project/IO/fileutils/a.txt

preVisitDirectory /Users/vincent/IDEA_Project/my_project/IO/fileutils
preVisitDirectory /Users/vincent/IDEA_Project/my_project/IO/fileutils/abc
visitFile /Users/vincent/IDEA_Project/my_project/IO/fileutils/abc/abc.txt
visitFile /Users/vincent/IDEA_Project/my_project/IO/fileutils/abc/a.txt
visitFile /Users/vincent/IDEA_Project/my_project/IO/fileutils/abc/abcd.txt
postVisitDirectory /Users/vincent/IDEA_Project/my_project/IO/fileutils/abc
visitFile /Users/vincent/IDEA_Project/my_project/IO/fileutils/io.png
visitFile /Users/vincent/IDEA_Project/my_project/IO/fileutils/a.txt
postVisitDirectory /Users/vincent/IDEA_Project/my_project/IO/fileutils

visitFile /Users/vincent/IDEA_Project/my_project/IO/fileutils/abc
visitFile /Users/vincent/IDEA_Project/my_project/IO/fileutils/io.png
visitFile /Users/vincent/IDEA_Project/my_project/IO/fileutils/a.txt

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