String 与 ByteBuffer的互转

 // 1 将字符串转为ByteBuffer
        ByteBuffer buffer = ByteBuffer.allocate(20);
        buffer.put("hello".getBytes());
        System.out.println(buffer);
        // 2 Charset
        ByteBuffer buffer1 = StandardCharsets.UTF_8.encode("hello");
        System.out.println(buffer1);
        // 3 wrap
        ByteBuffer buffer2 = ByteBuffer.wrap("hello".getBytes());
        System.out.println(buffer2);

        // 将ByteBuffer转为String
        String mes = StandardCharsets.UTF_8.decode(buffer2).toString();
        System.out.println(mes);

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Paths 与 Files 的使用

创建一级目录

try {
    Path path = Paths.get("hello");
     Files.createDirectory(path);
 } catch (IOException e) {
     e.printStackTrace();
 }
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如果目录已存在，会跑出异常 FileAireadyExistsException
不能创建多级目录，否在会抛出NosuchFileException

创建多级目录

try {
  	Path path = Paths.get("hello/3/3/2");
    Files.createDirectories(path);
} catch (IOException e) {
    e.printStackTrace();
  }
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文件拷贝

try {
            Path path = Paths.get("hello/1.txt");
            Path target = Paths.get("hello/2.txt");
            Files.copy(path,target);
        } catch (IOException e) {
            e.printStackTrace();
        }
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如果文件已经存在，则会抛异常FileAlreadyExistsException
如果希望覆盖，可以用重载的方法

try {
   Path path = Paths.get("hello/1.txt");
     Path target = Paths.get("hello/2.txt");
     Files.copy(path,target, StandardCopyOption.REPLACE_EXISTING);
 } catch (IOException e) {
     e.printStackTrace();
 }
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遍历文件

 AtomicInteger dirCount = new AtomicInteger();
        AtomicInteger fileCount = new AtomicInteger();
        try {
            Files.walkFileTree( Paths.get("/Users/mac/IdeaProjects/spring-demos"),new SimpleFileVisitor<Path>(){
                @Override
                public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) throws IOException {
                    dirCount.getAndIncrement();
                    return super.preVisitDirectory(dir, attrs);
                }

                @Override
                public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
                    if (file.toString().endsWith(".java")) {
                        fileCount.getAndIncrement();
                        System.out.println(file);
                    }
                    return super.visitFile(file, attrs);
                }
            });
        } catch (Exception e) {
            e.printStackTrace();
        }
        System.out.println("目录：" + dirCount + " java:" + fileCount);

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删除非空文件夹

try {
            Files.walkFileTree(Paths.get("/Users/mac/IdeaProjects/spring-demos/hello"),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);
                }
            });
        } catch (IOException e) {
            e.printStackTrace();
        }
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文件复制

 String source ="/Users/mac/Desktop/111";
        String target ="/Users/mac/Desktop/222";

        try {
            Files.walk(Paths.get(source)).forEach(path -> {
                try {
                    String targetName = path.toString().replace(source, target);
                    if (Files.isDirectory(path)) {
                        Files.createDirectory(Paths.get(targetName));
                    }else if(Files.isRegularFile(path)){
                        Files.copy(path,Paths.get(targetName));
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
            });
        } catch (IOException e) {
            e.printStackTrace();
        }
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