📅 最后修改于: 2020-09-27 07:38:17 🧑 作者: Mango
File类是文件和目录路径名的抽象表示。路径名可以是绝对路径，也可以是相对路径。
File类具有几种处理目录和文件的方法，例如创建新目录或文件，删除和重命名目录或文件，列出目录内容等。
| Modifier | Type | Field | Description |
|---|---|---|---|
| static | String | pathSeparator | It is system-dependent path-separator character, represented as a string for convenience. |
| static | char | pathSeparatorChar | It is system-dependent path-separator character. |
| static | String | separator | It is system-dependent default name-separator character, represented as a string for convenience. |
| static | char | separatorChar | It is system-dependent default name-separator character. |
| Constructor | Description |
|---|---|
| File(File parent, String child) | It creates a new File instance from a parent abstract pathname and a child pathname string. |
| File(String pathname) | It creates a new File instance by converting the given pathname string into an abstract pathname. |
| File(String parent, String child) | It creates a new File instance from a parent pathname string and a child pathname string. |
| File(URI uri) | It creates a new File instance by converting the given file: URI into an abstract pathname. |
| Modifier and Type | Method | Description |
|---|---|---|
| static File | createTempFile(String prefix, String suffix) | It creates an empty file in the default temporary-file directory, using the given prefix and suffix to generate its name. |
| boolean | createNewFile() | It atomically creates a new, empty file named by this abstract pathname if and only if a file with this name does not yet exist. |
| boolean | canWrite() | It tests whether the application can modify the file denoted by this abstract pathname.String[] |
| boolean | canExecute() | It tests whether the application can execute the file denoted by this abstract pathname. |
| boolean | canRead() | It tests whether the application can read the file denoted by this abstract pathname. |
| boolean | isAbsolute() | It tests whether this abstract pathname is absolute. |
| boolean | isDirectory() | It tests whether the file denoted by this abstract pathname is a directory. |
| boolean | isFile() | It tests whether the file denoted by this abstract pathname is a normal file. |
| String | getName() | It returns the name of the file or directory denoted by this abstract pathname. |
| String | getParent() | It returns the pathname string of this abstract pathname’s parent, or null if this pathname does not name a parent directory. |
| Path | toPath() | It returns a java.nio.file.Path object constructed from the this abstract path. |
| URI | toURI() | It constructs a file: URI that represents this abstract pathname. |
| File[] | listFiles() | It returns an array of abstract pathnames denoting the files in the directory denoted by this abstract pathname |
| long | getFreeSpace() | It returns the number of unallocated bytes in the partition named by this abstract path name. |
| String[] | list(FilenameFilter filter) | It returns an array of strings naming the files and directories in the directory denoted by this abstract pathname that satisfy the specified filter. |
| boolean | mkdir() | It creates the directory named by this abstract pathname. |
import java.io.*;
public class FileDemo {
public static void main(String[] args) {
try {
File file = new File("javaFile123.txt");
if (file.createNewFile()) {
System.out.println("New File is created!");
} else {
System.out.println("File already exists.");
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
输出：
New File is created!
import java.io.*;
public class FileDemo2 {
public static void main(String[] args) {
String path = "";
boolean bool = false;
try {
// createing new files
File file = new File("testFile1.txt");
file.createNewFile();
System.out.println(file);
// createing new canonical from file object
File file2 = file.getCanonicalFile();
// returns true if the file exists
System.out.println(file2);
bool = file2.exists();
// returns absolute pathname
path = file2.getAbsolutePath();
System.out.println(bool);
// if file exists
if (bool) {
// prints
System.out.print(path + " Exists? " + bool);
}
} catch (Exception e) {
// if any error occurs
e.printStackTrace();
}
}
}
输出：
testFile1.txt
/home/Work/Project/File/testFile1.txt
true
/home/Work/Project/File/testFile1.txt Exists? true
import java.io.*;
public class FileExample {
public static void main(String[] args) {
File f=new File("/Users/sonoojaiswal/Documents");
String filenames[]=f.list();
for(String filename:filenames){
System.out.println(filename);
}
}
}
输出：
"info.properties"
"info.properties".rtf
.DS_Store
.localized
Alok news
apache-tomcat-9.0.0.M19
apache-tomcat-9.0.0.M19.tar
bestreturn_org.rtf
BIODATA.pages
BIODATA.pdf
BIODATA.png
struts2jars.zip
workspace
import java.io.*;
public class FileExample {
public static void main(String[] args) {
File dir=new File("/Users/sonoojaiswal/Documents");
File files[]=dir.listFiles();
for(File file:files){
System.out.println(file.getName()+" Can Write: "+file.canWrite()+"
Is Hidden: "+file.isHidden()+" Length: "+file.length()+" bytes");
}
}
}
输出：
"info.properties" Can Write: true Is Hidden: false Length: 15 bytes
"info.properties".rtf Can Write: true Is Hidden: false Length: 385 bytes
.DS_Store Can Write: true Is Hidden: true Length: 36868 bytes
.localized Can Write: true Is Hidden: true Length: 0 bytes
Alok news Can Write: true Is Hidden: false Length: 850 bytes
apache-tomcat-9.0.0.M19 Can Write: true Is Hidden: false Length: 476 bytes
apache-tomcat-9.0.0.M19.tar Can Write: true Is Hidden: false Length: 13711360 bytes
bestreturn_org.rtf Can Write: true Is Hidden: false Length: 389 bytes
BIODATA.pages Can Write: true Is Hidden: false Length: 707985 bytes
BIODATA.pdf Can Write: true Is Hidden: false Length: 69681 bytes
BIODATA.png Can Write: true Is Hidden: false Length: 282125 bytes
workspace Can Write: true Is Hidden: false Length: 1972 bytes