Java 输入/输出——File类 / 憋错料

　　File类是java.io包下代表与平台无关的文件和目录，也就是说，如果希望在程序中操作文件和目录，都可以通过File类来完成。值得指出的是，不管是文件还是目录都是使用File来操作的，File能新建、删除、重命名文件和目录，File不能访问文件内容本身。如果需要访问文件内容本身，则需要使用输入/输出流。

　　File类相关的方法参考链接：https://docs.oracle.com/javase/9/docs/api/overview-summary.html

Field Summary

Fields
Modifier and Type	Field	Description
`static String`	`pathSeparator`	The system-dependent path-separator character, represented as a string for convenience.
`static char`	`pathSeparatorChar`	The system-dependent path-separator character.
`static String`	`separator`	The system-dependent default name-separator character, represented as a string for convenience.
`static char`	`separatorChar`	The system-dependent default name-separator character.

Constructor Summary

Constructors
Constructor	Description
`File?(File parent, String child)`	Creates a new `File` instance from a parent abstract pathname and a child pathname string.
`File?(String pathname)`	Creates a new `File` instance by converting the given pathname string into an abstract pathname.
`File?(String parent, String child)`	Creates a new `File` instance from a parent pathname string and a child pathname string.
`File?(URI uri)`	Creates a new `File` instance by converting the given `file:` URI into an abstract pathname.

Method Summary

All MethodsStatic Methods Instance Methods Concrete Methods Deprecated Methods
Modifier and Type	Method	Description
`boolean`	`canExecute?()`	Tests whether the application can execute the file denoted by this abstract pathname.
`boolean`	`canRead?()`	Tests whether the application can read the file denoted by this abstract pathname.
`boolean`	`canWrite?()`	Tests whether the application can modify the file denoted by this abstract pathname.
`int`	`compareTo?(File pathname)`	Compares two abstract pathnames lexicographically.
`boolean`	`createNewFile?()`	Atomically creates a new, empty file named by this abstract pathname if and only if a file with this name does not yet exist.
`static File`	`createTempFile?(String prefix,String suffix)`	Creates an empty file in the default temporary-file directory, using the given prefix and suffix to generate its name.
`static File`	`createTempFile?(String prefix,String suffix,File directory)`	Creates a new empty file in the specified directory, using the given prefix and suffix strings to generate its name.
`boolean`	`delete?()`	Deletes the file or directory denoted by this abstract pathname.
`void`	`deleteOnExit?()`	Requests that the file or directory denoted by this abstract pathname be deleted when the virtual machine terminates.
`boolean`	`equals?(Object obj)`	Tests this abstract pathname for equality with the given object.
`boolean`	`exists?()`	Tests whether the file or directory denoted by this abstract pathname exists.
`File`	`getAbsoluteFile?()`	Returns the absolute form of this abstract pathname.
`String`	`getAbsolutePath?()`	Returns the absolute pathname string of this abstract pathname.
`File`	`getCanonicalFile?()`	Returns the canonical form of this abstract pathname.
`String`	`getCanonicalPath?()`	Returns the canonical pathname string of this abstract pathname.
`long`	`getFreeSpace?()`	Returns the number of unallocated bytes in the partition named by this abstract path name.
`String`	`getName?()`	Returns the name of the file or directory denoted by this abstract pathname.
`String`	`getParent?()`	Returns the pathname string of this abstract pathname‘s parent, or `null` if this pathname does not name a parent directory.
`File`	`getParentFile?()`	Returns the abstract pathname of this abstract pathname‘s parent, or `null` if this pathname does not name a parent directory.
`String`	`getPath?()`	Converts this abstract pathname into a pathname string.
`long`	`getTotalSpace?()`	Returns the size of the partition named by this abstract pathname.
`long`	`getUsableSpace?()`	Returns the number of bytes available to this virtual machine on the partition named by this abstract pathname.
`int`	`hashCode?()`	Computes a hash code for this abstract pathname.
`boolean`	`isAbsolute?()`	Tests whether this abstract pathname is absolute.
`boolean`	`isDirectory?()`	Tests whether the file denoted by this abstract pathname is a directory.
`boolean`	`isFile?()`	Tests whether the file denoted by this abstract pathname is a normal file.
`boolean`	`isHidden?()`	Tests whether the file named by this abstract pathname is a hidden file.
`long`	`lastModified?()`	Returns the time that the file denoted by this abstract pathname was last modified.
`long`	`length?()`	Returns the length of the file denoted by this abstract pathname.
`String[]`	`list?()`	Returns an array of strings naming the files and directories in the directory denoted by this abstract pathname.
`String[]`	`list?(FilenameFilter filter)`	Returns an array of strings naming the files and directories in the directory denoted by this abstract pathname that satisfy the specified filter.
`File[]`	`listFiles?()`	Returns an array of abstract pathnames denoting the files in the directory denoted by this abstract pathname.
`File[]`	`listFiles?(FileFilter filter)`	Returns an array of abstract pathnames denoting the files and directories in the directory denoted by this abstract pathname that satisfy the specified filter.
`File[]`	`listFiles?(FilenameFilter filter)`	Returns an array of abstract pathnames denoting the files and directories in the directory denoted by this abstract pathname that satisfy the specified filter.
`static File[]`	`listRoots?()`	List the available filesystem roots.
`boolean`	`mkdir?()`	Creates the directory named by this abstract pathname.
`boolean`	`mkdirs?()`	Creates the directory named by this abstract pathname, including any necessary but nonexistent parent directories.
`boolean`	`renameTo?(File dest)`	Renames the file denoted by this abstract pathname.
`boolean`	`setExecutable?(boolean executable)`	A convenience method to set the owner‘s execute permission for this abstract pathname.
`boolean`	`setExecutable?(boolean executable, boolean ownerOnly)`	Sets the owner‘s or everybody‘s execute permission for this abstract pathname.
`boolean`	`setLastModified?(long time)`	Sets the last-modified time of the file or directory named by this abstract pathname.
`boolean`	`setReadable?(boolean readable)`	A convenience method to set the owner‘s read permission for this abstract pathname.
`boolean`	`setReadable?(boolean readable, boolean ownerOnly)`	Sets the owner‘s or everybody‘s read permission for this abstract pathname.
`boolean`	`setReadOnly?()`	Marks the file or directory named by this abstract pathname so that only read operations are allowed.
`boolean`	`setWritable?(boolean writable)`	A convenience method to set the owner‘s write permission for this abstract pathname.
`boolean`	`setWritable?(boolean writable, boolean ownerOnly)`	Sets the owner‘s or everybody‘s write permission for this abstract pathname.
`Path`	`toPath?()`	Returns a `java.nio.file.Path` object constructed from the this abstract path.
`String`	`toString?()`	Returns the pathname string of this abstract pathname.
`URI`	`toURI?()`	Constructs a `file:` URI that represents this abstract pathname.
`URL`	`toURL?()`	Deprecated. This method does not automatically escape characters that are illegal in URLs. It is recommended that new code convert an abstract pathname into a URL by first converting it into a URI, via the `toURI`method, and then converting the URI into a URL via the `URI.toURL` method.

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

 1 package com.zyjhandsome.io;
 2
 3 import java.io.*;
 4
 5 public class FileTest {
 6
 7     public static void main(String[] args) throws IOException
 8     {
 9         // 以当前路径来创建一个File对象
10         File file = new File(".");
11         // 直接获取文件名, 输出一点
12         System.out.println(file.getName());
13         // 获取相对路径的父路径可能出错, 下面代码输出null
14         System.out.println(file.getParent());
15         // 获取绝对路径
16         System.out.println(file.getAbsoluteFile());
17         // 获取绝对路径
18         System.out.println(file.getAbsoluteFile().getParent());
19         // 当前路径下创建一个临时文件
20         File tmpFile = File.createTempFile("aaa", ".txt", file);
21         // 指定当JVM退出时候删除该文件
22         tmpFile.deleteOnExit();
23         // 以系统当前时间作为新文件名来创建新文件
24         File newFile = new File(System.currentTimeMillis() + "");
25         System.out.println("newFile对象是否存在1: " + newFile.exists());
26         // 以指定newFile对象来创建一个文件
27         newFile.createNewFile();
28         System.out.println("newFile对象是否存在2: " + newFile.exists());
29         // 以newFile对象来创建一个目录，因为newFile已经存在，所以下面方法返回false, 即无法创建该目录
30         System.out.println("newFile.mkdir():" + newFile.mkdir());
31         System.out.println("----------------------");
32         // 使用list()方法列出当前路径下的所有文件和路径
33         String[] fileList = file.list();
34         for (String fileName : fileList)
35         {
36             System.out.println(fileName);
37         }
38         System.out.println("----------------------");
39         // listRoots()静态方法列出所有的磁盘根路径
40         File[] roots = File.listRoots();
41         System.out.println("====系统所有根路径如下====");
42         for (File root : roots)
43         {
44             System.out.println(root);
45         }
46     }
47 }

原文地址：https://www.cnblogs.com/zyjhandsome/p/9694039.html

时间： 2024-12-15 07:12:49

Java 输入/输出——File类

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

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