JDK7文件处理
2016-04-30 14:46
701 查看
实用的工具类,Path,Paths,Files,FileSystem
有一些很灵活的处理方法: [java] view
plain copy
//得到一个Path对象
Path path = Paths.get("/test/a.txt");
//Path转换File
File file = path.toFile();
Files.readAllBytes(path);
Files.deleteIfExists(path);
Files.size(path);
正确拼接路径不要手动拼接路径
不好的代码: [java] view
plain copy
String game = "foo";
File file = new File("~/test/" + game + ".txt");
即使是要手动拼接路径,请使用下面两个平台无关的变量:
[java] view
plain copy
System.out.println(File.pathSeparator);
System.out.println(File.separator);
正确简洁的方法是使用Paths类:
[java] view
plain copy
Path path = Paths.get("~/test/", "foo", "bar", "a.txt");
System.out.println(path);
// ~/test/foo/bar/a.txt
读取文件的所有内容,文件的所有行
读取文件所有内容前,先判断文件大小,防止OOM。 [java] view
plain copy
public static byte[] readAllBytes(String fileName, long maxSize) throws IOException {
Path path = Paths.get(fileName);
long size = Files.size(path);
if (size > maxSize) {
throw new IOException("file: " + path + ", size:" + size + "> " + maxSize);
}
return Files.readAllBytes(path);
}
public static List<String> readAlllines(String fileName, Charset charset, long maxSize) throws IOException {
Path path = Paths.get(fileName);
long size = Files.size(path);
if (size > maxSize) {
throw new IOException("file: " + path + ", size:" + size + "> " + maxSize);
}
return Files.readAllLines(path, charset);
}
利用JDK7的特性,auto close,远离一堆的catch, close
[java] viewplain copy
Path path = Paths.get("~/test/", "foo", "bar", "a.txt");
try (InputStream in = Files.newInputStream(path)) {
// process
//in.read();
}
历遍目录
DK7新特性,FileVisitor [java] view
plain copy
public class MyFileVisitor extends SimpleFileVisitor<Path>{
@Override
public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
System.out.println(file);
return FileVisitResult.CONTINUE;
}
public static void main(String[] args) throws IOException {
Path path = Paths.get("/home/user/test");
Files.walkFileTree(path, new MyFileVisitor());
}
}
判断文件是否在父路径下
网上流传一种递归判断parent的方式,http://stackoverflow.com/questions/18227634/check-if-file-is-in-subdirectory但是查阅jdk代码后,发现getParent()函数是通过处理文件名得到的。所以直接比较文件前缀即可。
请务必注意,file.getCanonicalPath()函数 。
[java] view
plain copy
public static boolean isSubFile(File parent, File child) throws IOException {
return child.getCanonicalPath().startsWith(parent.getCanonicalPath());
}
public static boolean isSubFile(String parent, String child) throws IOException {
return isSubFile(new File(parent), new File(child));
}
相关文章推荐
- JDK动态代理VS CgLib
- Ubuntu 安装 JDK 问题
- jdk与jre的区别 很形象,很清晰,通俗易懂
- jdk中String类设计成final的原由
- win7下安装 JDK 基本流程
- jdk环境变量配置
- win2003 jsp运行环境架设心得(jdk+tomcat)
- windows linux jdk安装配置方法
- Java编程之jdk1.4,jdk1.5和jdk1.6的区别分析(经典)
- 详解JDK 5 Annotation 注解之@Target的用法介绍
- 简单记录Cent OS服务器配置JDK+Tomcat+MySQL
- Android开发的IDE、ADT、SDK、JDK、NDK等名词解释
- Java4Android开发教程(一)JDK安装与配置
- Eclipse配置Tomcat和JDK步骤图解
- java中sdk与jdk的区别详细解析
- JDK 5 提供的注解:Target、Inherited和Documented的区别
- jdk中密钥和证书管理工具keytool常用命令详解
- 在RedHat系统上安装JDK与Tomcat的步骤
- 在Ubuntu系统下安装JDK和Tomcat的教程
- java动态代理(jdk与cglib)详细解析