A Path represents a path that is hierarchical and composed of a sequence of directory and file name elements separated by a special separator or delimiter.

Path用于来表示文件路径和文件。可以有多种方法来构造一个Path对象来表示一个文件路径，或者一个文件：

1)首先是final类Paths的两个static方法，如何从一个路径字符串来构造Path对象：

Path path1 = Paths.get("C:/", "Xmp");

Path path2 = Paths.get("C:/Xmp");

Path path3 = Paths.get(URI.create("file:///C:/Xmp/dd"));

2)FileSystems构造：

Path path4 = FileSystems.getDefault().getPath("C:/", "access.log");

3)File和Path之间的转换，File和URI之间的转换：

File file = new File("C:/my.ini");

Path p1 =file.toPath();

p1.toFile();

file.toURI();

4)创建一个文件：

Path target2 = Paths.get("C:\\mystuff.txt");

//Set perms = PosixFilePermissions.fromString("rw-rw-rw-");

//FileAttribute> attrs = PosixFilePermissions.asFileAttribute(perms);

try{

if(!Files.exists(target2))

Files.createFile(target2);

} catch(IOException e) {

e.printStackTrace();

}

windows下不支持PosixFilePermission来指定rwx权限。

5)Files.newBufferedReader读取文件：

try{

//Charset.forName("GBK")

BufferedReader reader = Files.newBufferedReader(Paths.get("C:\\my.ini"), StandardCharsets.UTF_8);

String str = null;

while((str = reader.readLine()) != null){

System.out.println(str);

}

} catch(IOException e) {

e.printStackTrace();

}

可以看到使用 Files.newBufferedReader 远比原来的FileInputStream，然后BufferedReader包装，等操作简单的多了。

这里如果指定的字符编码不对，可能会抛出异常 MalformedInputException ，或者读取到了乱码：

java.nio.charset.MalformedInputException: Input length = 1at java.nio.charset.CoderResult.throwException(CoderResult.java:281)

at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:339)

at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:178)

at java.io.InputStreamReader.read(InputStreamReader.java:184)

at java.io.BufferedReader.fill(BufferedReader.java:161)

at java.io.BufferedReader.readLine(BufferedReader.java:324)

at java.io.BufferedReader.readLine(BufferedReader.java:389)

at com.coin.Test.main(Test.java:79)

6)文件写操作：

try{

BufferedWriter writer = Files.newBufferedWriter(Paths.get("C:\\my2.ini"), StandardCharsets.UTF_8);

writer.write("测试文件写操作");

writer.flush();

writer.close();

} catch(IOException e1) {

e1.printStackTrace();

}

7)遍历一个文件夹：

Path dir = Paths.get("D:\\webworkspace");

try(DirectoryStream stream =Files.newDirectoryStream(dir)){

for(Path e : stream){

System.out.println(e.getFileName());

}

}catch(IOException e){

}

try (Stream stream = Files.list(Paths.get("C:/"))){

Iterator ite =stream.iterator();

while(ite.hasNext()){

Path pp =ite.next();

System.out.println(pp.getFileName());

}

} catch(IOException e) {

e.printStackTrace();

}

上面是遍历单个目录，它不会遍历整个目录。遍历整个目录需要使用：Files.walkFileTree

8)遍历整个文件目录：

public static void main(String[] args) throwsIOException{

Path startingDir = Paths.get("C:\\apache-tomcat-8.0.21");

List result = new LinkedList();

Files.walkFileTree(startingDir, newFindJavaVisitor(result));

System.out.println("result.size()=" +result.size());

}

private static class FindJavaVisitor extends SimpleFileVisitor{

private Listresult;

public FindJavaVisitor(Listresult){

this.result =result;

}

@Override

publicFileVisitResult visitFile(Path file, BasicFileAttributes attrs){

if(file.toString().endsWith(".java")){

result.add(file.getFileName());

}

returnFileVisitResult.CONTINUE;

}

}

来一个实际例子：

public static void main(String[] args) throwsIOException {

Path startingDir = Paths.get("F:\\upload\\images"); //F:\\upload\\images\\2\\20141206

List result = new LinkedList();

Files.walkFileTree(startingDir, newFindJavaVisitor(result));

System.out.println("result.size()=" +result.size());

System.out.println("done.");

}

private static class FindJavaVisitor extends SimpleFileVisitor{

private Listresult;

public FindJavaVisitor(Listresult){

this.result =result;

}

@Override

publicFileVisitResult visitFile(Path file, BasicFileAttributes attrs){

String filePath =file.toFile().getAbsolutePath();

if(filePath.matches(".*_[1|2]{1}\\.(?i)(jpg|jpeg|gif|bmp|png)")){

try{

Files.deleteIfExists(file);

} catch(IOException e) {

e.printStackTrace();

}

result.add(file.getFileName());

} returnFileVisitResult.CONTINUE;

}

}

将目录下面所有符合条件的图片删除掉：filePath.matches(".*_[1|2]{1}\\.(?i)(jpg|jpeg|gif|bmp|png)")

public static void main(String[] args) throwsIOException {

Path startingDir = Paths.get("F:\\111111\\upload\\images"); //F:\111111\\upload\\images\\2\\20141206

List result = new LinkedList();

Files.walkFileTree(startingDir, newFindJavaVisitor(result));

System.out.println("result.size()=" +result.size());

System.out.println("done.");

}

private static class FindJavaVisitor extends SimpleFileVisitor{

private Listresult;

public FindJavaVisitor(Listresult){

this.result =result;

}

@Override

publicFileVisitResult visitFile(Path file, BasicFileAttributes attrs){

String filePath =file.toFile().getAbsolutePath();

int width = 224;

int height = 300;

StringUtils.substringBeforeLast(filePath, ".");

String newPath = StringUtils.substringBeforeLast(filePath, ".") + "_1."

+ StringUtils.substringAfterLast(filePath, ".");

try{

ImageUtil.zoomImage(filePath, newPath, width, height);

} catch(IOException e) {

e.printStackTrace();

returnFileVisitResult.CONTINUE;

}

result.add(file.getFileName());

returnFileVisitResult.CONTINUE;

}

}

为目录下的所有图片生成指定大小的缩略图。a.jpg 则生成 a_1.jpg

2. 强大的java.nio.file.Files

1)创建目录和文件：

try{

Files.createDirectories(Paths.get("C://TEST"));

if(!Files.exists(Paths.get("C://TEST")))

Files.createFile(Paths.get("C://TEST/test.txt"));

//Files.createDirectories(Paths.get("C://TEST/test2.txt"));

} catch(IOException e) {

e.printStackTrace();

}

注意创建目录和文件Files.createDirectories 和 Files.createFile不能混用，必须先有目录，才能在目录中创建文件。

2)文件复制:

从文件复制到文件：Files.copy(Path source, Path target, CopyOption options);

从输入流复制到文件：Files.copy(InputStream in, Path target, CopyOption options);

从文件复制到输出流：Files.copy(Path source, OutputStream out);

try{

Files.createDirectories(Paths.get("C://TEST"));

if(!Files.exists(Paths.get("C://TEST")))

Files.createFile(Paths.get("C://TEST/test.txt"));

//Files.createDirectories(Paths.get("C://TEST/test2.txt"));

Files.copy(Paths.get("C://my.ini"), System.out);

Files.copy(Paths.get("C://my.ini"), Paths.get("C://my2.ini"), StandardCopyOption.REPLACE_EXISTING);

Files.copy(System.in, Paths.get("C://my3.ini"), StandardCopyOption.REPLACE_EXISTING);

} catch(IOException e) {

e.printStackTrace();

}

3)遍历一个目录和文件夹上面已经介绍了：Files.newDirectoryStream ， Files.walkFileTree

4)读取文件属性：

Path zip =Paths.get(uri);

System.out.println(Files.getLastModifiedTime(zip));

System.out.println(Files.size(zip));

System.out.println(Files.isSymbolicLink(zip));

System.out.println(Files.isDirectory(zip));

System.out.println(Files.readAttributes(zip, "*"));

5)读取和设置文件权限：

Path profile = Paths.get("/home/digdeep/.profile");

PosixFileAttributes attrs = Files.readAttributes(profile, PosixFileAttributes.class);// 读取文件的权限

Set posixPermissions =attrs.permissions();

posixPermissions.clear();

String owner =attrs.owner().getName();

String perms =PosixFilePermissions.toString(posixPermissions);

System.out.format("%s %s%n", owner, perms);

posixPermissions.add(PosixFilePermission.OWNER_READ);

posixPermissions.add(PosixFilePermission.GROUP_READ);

posixPermissions.add(PosixFilePermission.OTHERS_READ);

posixPermissions.add(PosixFilePermission.OWNER_WRITE);

Files.setPosixFilePermissions(profile, posixPermissions); //设置文件的权限

Files类简直强大的一塌糊涂，几乎所有文件和目录的相关属性，操作都有想要的api来支持。这里懒得再继续介绍了，详细参见 jdk8 的文档。

一个实际例子：

importjava.io.BufferedReader;

importjava.io.BufferedWriter;

importjava.nio.charset.StandardCharsets;

importjava.nio.file.Files;

importjava.nio.file.Path;

importjava.nio.file.Paths;

public classStringTools {

public static voidmain(String[] args) {

try{

BufferedReader reader = Files.newBufferedReader(Paths.get("C:\\Members.sql"), StandardCharsets.UTF_8);

BufferedWriter writer = Files.newBufferedWriter(Paths.get("C:\\Members3.txt"), StandardCharsets.UTF_8);

String str = null;

while ((str = reader.readLine()) != null) {

if (str != null && str.indexOf(", CAST(0x") != -1 && str.indexOf("AS DateTime)") != -1) {

String newStr = str.substring(0, str.indexOf(", CAST(0x")) + ")";

writer.write(newStr);

writer.newLine();

}

}

writer.flush();

writer.close();

} catch(Exception e) {

e.printStackTrace();

}

}

}

场景是，sql server导出数据时，会将 datatime 导成16进制的binary格式，形如：, CAST(0x0000A2A500FC2E4F AS DateTime))

所以上面的程序是将最后一个 datatime 字段导出的 , CAST(0x0000A2A500FC2E4F AS DateTime) 删除掉，生成新的不含有datetime字段值的sql 脚本。用来导入到mysql中。

做到半途，其实有更好的方法，使用sql yog可以很灵活的将sql server中的表以及数据导入到mysql中。使用sql server自带的导出数据的功能，反而不好处理。