Java File Class

A File class in Java is an abstract representation of file and directory pathnames(e.g., c:/Programs/SampleFile.txt). Here Programs is a directory and SampleFile is a file.

The first name in an abstract pathname may be a directory name or, in the case of Microsoft Windows UNC pathnames, a hostname. Each subsequent name in an abstract pathname denotes a directory; the last name may denote either a directory or a file.
Examples :
C:\Program Files\Java
E:\Files\SampleFile.txt
hostname:/directorypath/resource
Instances of the File class are immutable; that is, once created, the abstract pathname represented by a File object will never change.

Constructors :

Constructor	Description
`public File(String pathname)`	Creates a new File instance by converting the given pathname string into an abstract pathname. If the given string is the empty string, then the result is the empty abstract pathname.
`File(String parent, String child)`	Creates a new File instance from a parent pathname string and a child pathname string.

Important Methods

Method	Description
`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.
`boolean exists()`	Tests whether the file or directory denoted by this abstract pathname exists.
`boolean isFile()`	Tests whether the file denoted by this abstract pathname is a normal file.
`boolean isDirectory()`	Tests whether the file denoted by this abstract pathname is a directory.
`boolean canExecute()`	Tests whether the application can execute the file denoted by this abstract pathname.
`boolean canWrite()`	Tests whether the application can modify the file denoted by this abstract pathname.
`boolean canRead()`	Tests whether the application can read the file denoted by this abstract pathname.
`boolean setExecutable(boolean executable)`	This is a convenience method to set the owner's execute 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)`	This is a convenience method to set the owner's write permission for this abstract pathname.
`String getPath()`	Converts this abstract pathname into a pathname string.
`String getName()`	Returns the name of the file or directory denoted by this abstract pathname.
`boolean delete()`	Deletes the file or directory denoted by this abstract pathname.
`boolean mkdirs()`	Creates the directory named by this abstract pathname, including any necessary but nonexistent parent directories.

FileDemo

CODE

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import java.io.*;

class CreatingFilesandFolders
{
    public static void main(String[] args) throws IOException
    {
        File folder = new File("E:JavaPrograms\\FolderOne\\"); // LINE A
    
        if(folder.mkdirs()) // LINE B
            System.out.println("Folder created.");
        else if(folder.exists()) // LINE C
            System.out.println("Folder already exists.");
        System.out.println(folder.getPath()); // LINE D
    
        File fileOne = new File(folder, "fileOne.txt"); // LINE E
        File fileTwo = new File(folder, "fileTwo.txt"); // LINE F
        
        if(fileOne.createNewFile() && fileTwo.createNewFile()) // LINE G
            System.out.println("Files created.");
        
        else if(fileOne.exists() && fileTwo.exists())
            System.out.println("files already exists");
        System.out.println(fileOne.getPath() + "\n" + fileTwo.getPath()); // LINE H
                                                                            
    }

}

OUTPUT

Folder created.
E:JavaPrograms\FolderOne
Files created.
E:JavaPrograms\FolderOne\fileOne.txt
E:JavaPrograms\FolderOne\fileTwo.txt

DESCRIPTION

At LINE A we are creating an absolute path string for folder.
At LINE B we are creating folder here mkdirs create folders and returns true if the folders are created otherwise false.
At LINE C we are checking whether the folder already exists.
At LINE D we are printing the path of folder.
At LINE E and LINE F we are creating absolute path for files.
At LINE G we are creating files using createNewFile.
At LINE H we are printing the file paths.

THINGS TO TRY

Create one more folder FolderTwo in JavaPrograms folder.

Create two more files fileThree and fileFour in FolderTwo.

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FilePermissionsDemo

CODE

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import java.io.*;

class FileOperationsDemo
{
    public static void main(String[] args) throws IOException
    {
        File sampleFile = new File("E:JavaPrograms\\FolderOne\\sampleFile.txt");
        if(sampleFile.createNewFile())                     // LINE A
            System.out.println("File created.");
        else
            System.out.println("File not created.");
        
        System.out.println("Default permissions for a newly created file.");
        System.out.println("IsFile        : " + sampleFile.isFile()); // LINE B
        System.out.println("CanRead    : " + sampleFile.canRead());    // LINE C
        System.out.println("CanWrite   : " + sampleFile.canWrite());   // LINE D
        System.out.println("CanExecute : " + sampleFile.canExecute()); // LINE E
    
        System.out.println("Changing file permissions.");
         // LINE F                                   
        System.out.println("Can set to non readable   : " + sampleFile.setReadable(false)); 
        // LINE G                                
        System.out.println("Can set to non writable   : " + sampleFile.setWritable(false)); 
        // LINE H                                
        System.out.println("Can set to non Executable : " + sampleFile.setExecutable(false)); 
    }
}

OUTPUT

File created.
Default permissions for a newly created file.
IsFile        : true
CanRead    : true
CanWrite   : false
CanExecute : true
Changing file permissions.
Can set to non readable   : false
Can set to non writable   : true
Can set to non Executable : false

DESCRIPTION

At LINE A we have created a sampleFile.
At LINE B we are checking whether sampleFile is a File or not.
At LINE C we are checking whether sampleFile is readable.
At LINE D we are checking whether sampleFile is writable.
At LINE E we are checking whether sampleFile is executable.
At LINE F we are checking whether we can set sampleFile to non readable.
At LINE G we are checking whether we can set sampleFile to non writable.
At LINE F we are checking whether we can set sampleFile to non executable.

THINGS TO TRY

Find the path of sampleFile using getPath method.

Delete sampleFile file.

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Rest of Methods :

Method	Description
`int compareTo(File pathname)`	compares two abstract pathnames lexicographically.
`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.
`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.
`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 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.
`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 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()`	lists the available filesystem roots.
`boolean mkdir()`	Creates the directory named by this abstract pathname.
`boolean renameTo(File dest)`	Renames the file denoted by 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)`	This is 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 setWritable(boolean writable, boolean ownerOnly)`	Sets the owner's or everybody's write permission for this abstract pathname.
`String toString()`	Returns the pathname string of this abstract pathname.
`URI toURI()`	Constructs a file: URI that represents this abstract pathname.