Java文件操作工具类

Paths

jdk7 引入了 Path 和 Paths 类

  • Path 用来表示文件路径
  • Paths 是工具类，用来获取 Path 实例
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Path source = Paths.get("1.txt"); // 相对路径 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

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

例子：

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Path path = Paths.get("d:\\data\\projects\\a\\..\\b");
System.out.println(path);
System.out.println(path.normalize()); // 正常化路径

会输出

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d:\data\projects\a\..\b
d:\data\projects\b

Files

Files 是 Java 中用于操作文件和目录的工具类之一。它提供了许多静态方法，用于执行文件和目录的创建、复制、移动、删除等操作。

使用例子

检查文件是否存在

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Path path = Paths.get("helloword/data.txt");
System.out.println(Files.exists(path));

创建一级目录

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Path path = Paths.get("helloword/d1");
Files.createDirectory(path);
  • 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

创建多级目录用

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Path path = Paths.get("helloword/d1/d2");
Files.createDirectories(path);

拷贝文件

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Path source = Paths.get("helloword/data.txt");
Path target = Paths.get("helloword/target.txt");
Files.copy(source, target);
  • 如果文件已存在，会抛异常 FileAlreadyExistsException

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

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Path source = Paths.get("helloword/data.txt");
Path target = Paths.get("helloword/data.txt");

Files.move(source, target, StandardCopyOption.ATOMIC_MOVE);
  • StandardCopyOption.ATOMIC_MOVE 保证文件移动的原子性

删除文件

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Path target = Paths.get("helloword/target.txt");

Files.delete(target);
  • 如果文件不存在，会抛异常 NoSuchFileException

删除目录

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Path target = Paths.get("helloword/d1");

Files.delete(target);
  • 如果目录还有内容，会抛异常 DirectoryNotEmptyException

遍历目录文件

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public static void main(String[] args) throws IOException {
    Path path = Paths.get("C:\\Program Files\\Java\\jdk1.8.0_91");
    AtomicInteger dirCount = new AtomicInteger();
    AtomicInteger fileCount = new AtomicInteger();
    Files.walkFileTree(path, new SimpleFileVisitor<Path>(){
        @Override
        public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) 
            throws IOException {
            System.out.println(dir);
            dirCount.incrementAndGet();
            return super.preVisitDirectory(dir, attrs);
        }

        @Override
        public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) 
            throws IOException {
            System.out.println(file);
            fileCount.incrementAndGet();
            return super.visitFile(file, attrs);
        }
    });
    System.out.println(dirCount); // 133
    System.out.println(fileCount); // 1479
}

统计 jar 的数目

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Path path = Paths.get("C:\\Program Files\\Java\\jdk1.8.0_91");
AtomicInteger fileCount = new AtomicInteger();
Files.walkFileTree(path, new SimpleFileVisitor<Path>(){
    @Override
    public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) 
        throws IOException {
        if (file.toFile().getName().endsWith(".jar")) {
            fileCount.incrementAndGet();
        }
        return super.visitFile(file, attrs);
    }
});
System.out.println(fileCount); // 724

删除多级目录

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Path path = Paths.get("d:\\a");
Files.walkFileTree(path, new SimpleFileVisitor<Path>(){
    @Override
    public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) 
        throws IOException {
        Files.delete(file);
        return super.visitFile(file, attrs);
    }

    @Override
    public FileVisitResult postVisitDirectory(Path dir, IOException exc) 
        throws IOException {
        Files.delete(dir);
        return super.postVisitDirectory(dir, exc);
    }
});

拷贝多级目录

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long start = System.currentTimeMillis();
String source = "D:\\Snipaste-1.16.2-x64";
String target = "D:\\Snipaste-1.16.2-x64aaa";

Files.walk(Paths.get(source)).forEach(path -> {
    try {
        String targetName = path.toString().replace(source, target);
        // 是目录
        if (Files.isDirectory(path)) {
            Files.createDirectory(Paths.get(targetName));
        }
        // 是普通文件
        else if (Files.isRegularFile(path)) {
            Files.copy(path, Paths.get(targetName));
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
});
long end = System.currentTimeMillis();
System.out.println(end - start);