IO Tutorial

IO Tutorial

IO stand for input and output.

IO is an API provided by Java that is used to read data from Input Devices and write data into Output Devices.

Using IO you can exchange the information from one device to another device.

IO API exist in java.io package.

IO can be divided into two parts:

1. File Handling
2. IO Stream

1. File Handling

In File Handling you can learn how to create a folder , file , delete a folder or file etc.

IO package provide a predefine class for file handling that name is File.

File class provide several following methods:

Type	Name & Description
boolean	canExecute(); Test whether the file is executable or not.
boolean	canRead(); Test whether the file is readable or not.
boolean	canWrite(); Test whether the file is writable or not.
boolean	createNewFile(); This method is used to create a blank file.
boolean	delete(); This method is used to delete a file.
void	deleteOnExit(); This method is used to delete file when JVM is shutdown.
boolean	exists(); Test whether the file is exists or not.
File	getAbsoluteFile(); Returns the absolute path of a file.
String	getAbsolutePath(); Returns the absolute path of a file.
File	getCanonicalFile(); Returns the canonical path of a file.
String	getCanonicalPath(); Returns the canonical path of a file.
long	getFreeSpace(); Returns the number of unallocated bytes in the partition name by this abstract path name.
String	getName(); Returns the file name.
String	getParent(); Returns the parent directory of this file name.
File	getParentFile(); Returns the parent directory of this file name.
String	getPath(); Convert this abstract pathname into a pathname string.
long	getTotalSpace(); Returns the total size of this abstract path name.
long	getUsableSpace(); Returns the available bytes of this abstract path name.
boolean	isAbsolute(); Test whether this path name is absolute or not.
boolean	isDirectory(); Test whether this path name is directory or not.
boolean	isFile(); Test this is a file or not.
boolean	isHidden(); Test this file is hidden or not.
long	lastModified(); Returns the time was last modified.
long	length(); Returns the length of this file.
String []	list(); Returns the list of files and directories.
String []	list(FilenameFilter filenamefilter); Returns the list of files and directories based on filters.
File []	listFiles(); Returns the list of files and directories.
File []	listFiles(FileFilter filefilter); Returns the list of files and directories based on filters.
File []	listFiles(FilenameFilter filenamefilter); Returns the list of files and directories based on filters.
File []	listRoots(); Returns the list of roots in filesystem.
boolean	mkdir(); This method is used to create a folder.
boolean	mkdirs(); This method is used to create sub folders.
boolean	renameTo(File f); This method is used to rename a file.
boolean	setExecutable(boolean s); Mark a file as an executable.
boolean	setExecutable(boolean s1,boolean s2); Mark the owner's execute permission for this abstract path name.
boolean	setLastModified(long a); Set the lastmodified time of a file or directory.
boolean	setReadable(boolean a); Mark a file as a readable.
boolean	setReadable(boolean a,boolean b); Mark the owner's read permission for this abstract path name.
boolean	setReadOnly(); Mark as read only operations are allowed.
boolean	setWritable(boolean s); Mark a file as a writable.
boolean	setWritable(boolean s1,boolean s2); Mark the owner's write permission for this absolute path name.
java.net.URI	toURI(); Constructs a file to URI.

File Handling Examples

1. How to get list of drives.

import java.io.File;

    public class Test {
     public static void main(String[] args) {
      File[] files = File.listRoots();
      for (int i = 0; i < files.length; i++) {
       System.out.println(files[i]);
      }
     }
    }

Result : C:/
D:/

2. How to get list of files from a particular drive.

import java.io.File;
    import java.io.IOException;

    public class Test {
     public static void main(String[] args) throws IOException {
      File file = new File("C://");
      String [] files= file.list();
      for (int i = 0; i < files.length; i++) {
       System.out.println(files[i]);
      }
     }
    }

Result :
$Recycle.Bin
$WINDOWS.~BT
$Windows.~WS
....
....
Windows

3. How to check a file is directory or not.

import java.io.File;
    import java.io.IOException;

    public class Test {
     public static void main(String[] args) throws IOException {
      File file = new File("D://deep");
       System.out.println(file.isDirectory());
     }
    }

Result : true

4. How to check a file is file or not.

import java.io.File;
    import java.io.IOException;

    public class Test {
     public static void main(String[] args) throws IOException {
      File file = new File("D://deep");
       System.out.println(file.isFile());
     }
    }

Result : false

5. How to check a file is exist or not.

import java.io.File;
    import java.io.IOException;

    public class Test {
     public static void main(String[] args) throws IOException {
      File file = new File("D://deep/filedemo.txt");
       System.out.println(file.exists());
     }
    }

Result : true

6. How to create a folder or directory.

import java.io.File;
    import java.io.IOException;

    public class Test {
     public static void main(String[] args) throws IOException {
            File file = new File("D://deep");
            boolean b=file.mkdir();
   System.out.println(b);
     }
    }

Result : true

7. How to create a sub folder or directory.

import java.io.File;
    import java.io.IOException;

    public class Test {
     public static void main(String[] args) throws IOException {
            
            File file = new File("D://deep/java");
            boolean b=file.mkdirs();
            System.out.println(b);
            //or
            File f1 = new File("D://main");
            boolean b1=f1.mkdir();
            File f2=new File(f1,"java");
            boolean b2=f2.mkdir();
            System.out.println(b1+"\t"+b2);
     }
    }

Result : true
true true

8. How to create an empty file.

import java.io.File;
    import java.io.IOException;

    public class Test {
     public static void main(String[] args) throws IOException {
            
            File file = new File("D://deep/filename.txt");
            boolean b=file.createNewFile();
            System.out.println(b);
     }
    }

Result : true

9. How to get file name.

import java.io.File;
    import java.io.IOException;

    public class Test {
     public static void main(String[] args) throws IOException {
            
            File file = new File("D://deep/filename.txt");
            String name=file.getName();
            System.out.println(name);
     }
    }

Result : filename.txt

10. How to get absolute path of file.

import java.io.File;
    import java.io.IOException;

    public class Test {
     public static void main(String[] args) throws IOException {
            
            File file = new File("D://deep/filename.txt");
            String path=file.getAbsolutePath();
            System.out.println(path);
     }
    }

Result : D://deep/filename.txt

11. How to get lastmodified of a file.

import java.io.File;
    import java.io.IOException;

    public class Test {
     public static void main(String[] args) throws IOException {
            
            File file = new File("D://filename.txt");
            long mod=file.lastModified();
            System.out.println(mod);
     }
    }

Result : 1585984259029