1、Path

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
  ```java 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

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# 2、Files
**检查文件是否存在**
```java
Path path = Paths.get("helloword/data.txt");
System.out.println(Files.exists(path));

创建一级目录

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

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

拷贝文件

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

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

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**

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

 public static void visitDir(String targetDir) throws IOException {
        AtomicInteger dirCount = new AtomicInteger(0);
        AtomicInteger fileCount = new AtomicInteger(0);
        Files.walkFileTree(Paths.get(targetDir),new SimpleFileVisitor<>(){
            @Override
            public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) throws IOException {
                System.out.println("======>" + dir);
                dirCount.addAndGet(1);
                return super.preVisitDirectory(dir, attrs);
            }
            @Override
            public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
                System.out.println(file);
                fileCount.addAndGet(1);
                return super.visitFile(file, attrs);
            }
        });
        System.out.println("目录数量：" + dirCount);
        System.out.println("文件数量：" + fileCount);
    }

删除多级目录

public static void delDir(String targetDir) throws IOException {
        Files.walkFileTree(Paths.get(targetDir),new SimpleFileVisitor<>(){
            @Override
            public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) throws IOException {
                System.out.println("======>" + dir);
                return super.preVisitDirectory(dir, attrs);
            }
            @Override
            public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
                System.out.println(file);
                Files.delete(file);
                return super.visitFile(file, attrs);
            }
            @Override
            public FileVisitResult postVisitDirectory(Path dir, IOException exc) throws IOException {
                System.out.println("<======" + dir);
                Files.delete(dir);
                return super.postVisitDirectory(dir, exc);
            }
        });
    }

拷贝目录

 public static void copyDir(String sourceDir,String targetDir) throws IOException {
        Files.walk(Paths.get(sourceDir)).forEach(path -> {
            try {
                String newPath = path.toString().replace(sourceDir, targetDir);
                if(Files.isDirectory(path)){
                    Files.createDirectory(Paths.get(newPath));
                }else if(Files.isRegularFile(path)){
                    Files.copy(path,Paths.get(newPath));
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        });
    }