Java的File对象

朴灿烈づ我的快乐病毒、 2022-06-13 01:22 169阅读 0赞

File对象在Java开发中经常需要碰到，其构造方法大家都比较熟悉了：

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 <td><code><a rel="nofollow">File</a>(<a title="java.io 中的类" rel="nofollow">File</a>&nbsp;dir,<a title="java.lang 中的类" rel="nofollow">String</a>&nbsp;name)</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;使用File对象路径和文件名进行创建句柄</td> 
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 <td><code><a rel="nofollow">File</a>(<a title="java.lang 中的类" rel="nofollow">String</a>&nbsp;path)</code> &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 只使用路径创建句柄</td> 
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 <td><code><a rel="nofollow">File</a>(<a title="java.lang 中的类" rel="nofollow">String</a>&nbsp;dirPath,<a title="java.lang 中的类" rel="nofollow">String</a>&nbsp;name)</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;使用字符路径和文件名来创建句柄</td> 
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 <td><code><a rel="nofollow">File</a>(<a title="java.net 中的类" rel="nofollow">URI</a>&nbsp;uri)</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;使用URI路径来创建句柄</td> 
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在使用构造函数之后，这个File对象就存在了，你可以使用File.exists()来对其进行判断，存在则返回true。

Java使用介乎于UNIX和Windows的路径方法，前斜线“/”可以正确解释，而如果要使用反斜线“\\”则需要进行转义序列“\\\\”，才能被解释器正确解释。

很重要的一点就是，Java的File对象可以是文件也可以是文件夹。所以当你使用

File file=new File("/java")；后

你返回的是文件夹，但是你在后面加一句

File fileNext=new File("/java/text.txt");

file使用isFile();的返回值就会变成了false。它变成了文件夹，也就是“目录”。

对于目录属性的File，我们可以使用list()来显示目录下的内容。

其他方法摘要，可以参考以下文档

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 <th colspan="2" align="left">方法摘要</th> 
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 <td align="right"><code>&nbsp;boolean</code></td> 
 <td><code><a rel="nofollow">canRead</a>()</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Indicates whether the current context is allowed to read from this file.</td> 
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 <td align="right"><code>&nbsp;boolean</code></td> 
 <td><code><a rel="nofollow">canWrite</a>()</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Indicates whether the current context is allowed to write to this file.</td> 
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 <td align="right"><code>&nbsp;int</code></td> 
 <td><code><a rel="nofollow">compareTo</a>(<a title="java.io 中的类" rel="nofollow">File</a>&nbsp;another)</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Returns the relative sort ordering of the paths for this file and the file<code>another</code>.</td> 
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 <td align="right"><code>&nbsp;boolean</code></td> 
 <td><code><a rel="nofollow">createNewFile</a>()</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Creates a new, empty file on the file system according to the path information stored in this file.</td> 
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 <td align="right"><code>static&nbsp;<a title="java.io 中的类" rel="nofollow">File</a></code></td> 
 <td><code><a rel="nofollow">createTempFile</a>(<a title="java.lang 中的类" rel="nofollow">String</a>&nbsp;prefix,<a title="java.lang 中的类" rel="nofollow">String</a>&nbsp;suffix)</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Creates an empty temporary file using the given prefix and suffix as part of the file name.</td> 
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 <td align="right"><code>static&nbsp;<a title="java.io 中的类" rel="nofollow">File</a></code></td> 
 <td><code><a rel="nofollow">createTempFile</a>(<a title="java.lang 中的类" rel="nofollow">String</a>&nbsp;prefix,<a title="java.lang 中的类" rel="nofollow">String</a>&nbsp;suffix, <a title="java.io 中的类" rel="nofollow">File</a>&nbsp;directory)</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Creates an empty temporary file in the given directory using the given prefix and suffix as part of the file name.</td> 
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 <td align="right"><code>&nbsp;boolean</code></td> 
 <td><code><a rel="nofollow">delete</a>()</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Deletes this file.</td> 
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 <td align="right"><code>&nbsp;void</code></td> 
 <td><code><a rel="nofollow">deleteOnExit</a>()</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Schedules this file to be automatically deleted once the virtual machine terminates.</td> 
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 <td align="right"><code>&nbsp;boolean</code></td> 
 <td><code><a rel="nofollow">equals</a>(<a title="java.lang 中的类" rel="nofollow">Object</a>&nbsp;obj)</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Compares <code>obj</code> to this file and returns <code>true</code> if they represent thesame object using a path specific comparison.</td> 
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 <td align="right"><code>&nbsp;boolean</code></td> 
 <td><code><a rel="nofollow">exists</a>()</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Returns a boolean indicating whether this file can be found on the underlying file system.</td> 
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 <td align="right"><code>&nbsp;<a title="java.io 中的类" rel="nofollow">File</a></code></td> 
 <td><code><a rel="nofollow">getAbsoluteFile</a>()</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Returns a new file constructed using the absolute path of this file.</td> 
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 <td align="right"><code>&nbsp;<a title="java.lang 中的类" rel="nofollow">String</a></code></td> 
 <td><code><a rel="nofollow">getAbsolutePath</a>()</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Returns the absolute path of this file.</td> 
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 <td align="right"><code>&nbsp;<a title="java.io 中的类" rel="nofollow">File</a></code></td> 
 <td><code><a rel="nofollow">getCanonicalFile</a>()</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Returns a new file created using the canonical path of this file.</td> 
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 <td align="right"><code>&nbsp;<a title="java.lang 中的类" rel="nofollow">String</a></code></td> 
 <td><code><a rel="nofollow">getCanonicalPath</a>()</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Returns the absolute path of this file with all references resolved.</td> 
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 <td align="right"><code>&nbsp;<a title="java.lang 中的类" rel="nofollow">String</a></code></td> 
 <td><code><a rel="nofollow">getName</a>()</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Returns the name of the file or directory represented by this file.</td> 
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 <td align="right"><code>&nbsp;<a title="java.lang 中的类" rel="nofollow">String</a></code></td> 
 <td><code><a rel="nofollow">getParent</a>()</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Returns the pathname of the parent of this file.</td> 
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 <td align="right"><code>&nbsp;<a title="java.io 中的类" rel="nofollow">File</a></code></td> 
 <td><code><a rel="nofollow">getParentFile</a>()</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Returns a new file made from the pathname of the parent of this file.</td> 
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 <td align="right"><code>&nbsp;<a title="java.lang 中的类" rel="nofollow">String</a></code></td> 
 <td><code><a rel="nofollow">getPath</a>()</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Returns the path of this file.</td> 
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 <td align="right"><code>&nbsp;int</code></td> 
 <td><code><a rel="nofollow">hashCode</a>()</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Returns an integer hash code for the receiver.</td> 
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 <td align="right"><code>&nbsp;boolean</code></td> 
 <td><code><a rel="nofollow">isAbsolute</a>()</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Indicates if this file's pathname is absolute.</td> 
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 <td align="right"><code>&nbsp;boolean</code></td> 
 <td><code><a rel="nofollow">isDirectory</a>()</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Indicates if this file represents a directory on the underlying file system.</td> 
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 <td align="right"><code>&nbsp;boolean</code></td> 
 <td><code><a rel="nofollow">isFile</a>()</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Indicates if this file represents a file on the underlying file system.</td> 
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 <td align="right"><code>&nbsp;boolean</code></td> 
 <td><code><a rel="nofollow">isHidden</a>()</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Returns whether or not this file is a hidden file as defined by the operating system.</td> 
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 <td align="right"><code>&nbsp;long</code></td> 
 <td><code><a rel="nofollow">lastModified</a>()</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Returns the time when this file was last modified, measured in milliseconds since January 1st, 1970, midnight.</td> 
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 <td align="right"><code>&nbsp;long</code></td> 
 <td><code><a rel="nofollow">length</a>()</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Returns the length of this file in bytes.</td> 
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 <td align="right"><code>&nbsp;<a title="java.lang 中的类" rel="nofollow">String</a>[]</code></td> 
 <td><code><a rel="nofollow">list</a>()</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Returns an array of strings with the file names in the directory represented by this file.</td> 
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 <td align="right"><code>&nbsp;<a title="java.lang 中的类" rel="nofollow">String</a>[]</code></td> 
 <td><code><a rel="nofollow">list</a>(<a title="java.io 中的接口" rel="nofollow">FilenameFilter</a>&nbsp;filter)</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Gets a list of the files in the directory represented by this file.</td> 
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 <td align="right"><code>&nbsp;<a title="java.io 中的类" rel="nofollow">File</a>[]</code></td> 
 <td><code><a rel="nofollow">listFiles</a>()</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Returns an array of files contained in the directory represented by this file.</td> 
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 <td align="right"><code>&nbsp;<a title="java.io 中的类" rel="nofollow">File</a>[]</code></td> 
 <td><code><a rel="nofollow">listFiles</a>(<a title="java.io 中的接口" rel="nofollow">FileFilter</a>&nbsp;filter)</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Gets a list of the files in the directory represented by this file.</td> 
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 <td align="right"><code>&nbsp;<a title="java.io 中的类" rel="nofollow">File</a>[]</code></td> 
 <td><code><a rel="nofollow">listFiles</a>(<a title="java.io 中的接口" rel="nofollow">FilenameFilter</a>&nbsp;filter)</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Gets a list of the files in the directory represented by this file.</td> 
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 <td align="right"><code>static&nbsp;<a title="java.io 中的类" rel="nofollow">File</a>[]</code></td> 
 <td><code><a rel="nofollow">listRoots</a>()</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Lists the file system roots.</td> 
 </tr> 
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 <td align="right"><code>&nbsp;boolean</code></td> 
 <td><code><a rel="nofollow">mkdir</a>()</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Creates the directory named by the trailing filename of this file.</td> 
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 <td align="right"><code>&nbsp;boolean</code></td> 
 <td><code><a rel="nofollow">mkdirs</a>()</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Creates the directory named by the trailing filename of this file, including the complete directory path required to create this directory.</td> 
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 <td align="right"><code>&nbsp;boolean</code></td> 
 <td><code><a rel="nofollow">renameTo</a>(<a title="java.io 中的类" rel="nofollow">File</a>&nbsp;dest)</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Renames this file to the name represented by the <code>dest</code> file.</td> 
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 <td align="right"><code>&nbsp;boolean</code></td> 
 <td><code><a rel="nofollow">setLastModified</a>(long&nbsp;time)</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Sets the time this file was last modified, measured in milliseconds since January 1st, 1970, midnight.</td> 
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 <td align="right"><code>&nbsp;boolean</code></td> 
 <td><code><a rel="nofollow">setReadOnly</a>()</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Marks this file or directory to be read-only as defined by the operating system.</td> 
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 <td align="right"><code>&nbsp;<a title="java.lang 中的类" rel="nofollow">String</a></code></td> 
 <td><code><a rel="nofollow">toString</a>()</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Returns a string containing a concise, human-readable description of this file.</td> 
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 <td align="right"><code>&nbsp;<a title="java.net 中的类" rel="nofollow">URI</a></code></td> 
 <td><code><a rel="nofollow">toURI</a>()</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Returns a Uniform Resource Identifier for this file.</td> 
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 <td align="right"><code>&nbsp;<a title="java.net 中的类" rel="nofollow">URL</a></code></td> 
 <td><code><a rel="nofollow">toURL</a>()</code> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Returns a Uniform Resource Locator for this file.</td> 
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 </tbody> 
</table>