Java I/O Examples : How To Delete Temporary File

Intro

This examples will demonstrates how to delete a temporary file using Java program. To delete it, you can use one of the following method:

• deleteOnExit(), delete temporary file when program is terminated or exited.
• delete(), delete temporary file imediately,

Examples

package com.freesamplecode.java.io;

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

public class DeleteTemporaryFileDemo {
	public static void main(String[] args){
		
		try {
			
			// create temporary file "test.tmp"
			
			File tempFile = File.createTempFile("test", ".tmp");
			
			
			// delete temporary file when the program is terminated or existed
			
			tempFile.deleteOnExit();
			
			//delete temporary file immediately
			
            //tempFile.delete();
			
			System.out.println("Temporary file "+tempFile.getName() + " is successfully deleted");
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

Output

Temporary file test1195400416650249998.tmp is successfully deleted

Java I/O Examples : How To Generate A File Checksum Value With MD5 Algorithm

Intro

This examples will demonstrates how to generate a file checksum with MD5 algorithm. To generate it, you should use MessageDigest class. This output is in the hexadecimal format.

Examples

package com.freesamplecode.java.io;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class FileChecksumDemo {
	public static void main(String[] args){
		
		//Step 1 : prepare file name
		String fileName = "D:/temp/test/file_test.txt";
		
		try {
			
			//Step 2 : create MD5 MessageDigest object
			MessageDigest messageDigest = MessageDigest.getInstance("MD5");
			
			// Step 3 : read data
			FileInputStream fis = new FileInputStream(fileName);
			
			byte[] bytedata = new byte[1024];
			
			int read = 0;
			
			while((read = fis.read(bytedata)) != -1){
				messageDigest.update(bytedata, 0, read);
			}
			
			//Step 4: calculate digest bytedata 
			byte[] bytemd = messageDigest.digest();
			
			//Step 5 : convert into hex format
			
			StringBuffer sb = new StringBuffer("");
			
			for(int i = 0; i < bytemd.length; i++){
				sb.append(Integer.toString((bytemd[i] & 0xff) + 0x100, 16).substring(1));
			}
			
			//Step 6 : Display to console
			System.out.println("Result.....");
			System.out.println(fileName+" : " + sb.toString());
			
		} catch (NoSuchAlgorithmException e) {
			e.printStackTrace();
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
		
	}
}

Output

Result.....
D:/temp/test/file_test.txt : c16665a5040f355d62eea6d2d5274c83

Screenshot

Java I/O Examples : How To Move A File To Another Directory

Intro

This examples will demonstrates how to move a file from one directory to another directory. It's very tricky, we will use File.renameTo() method to move it.

Examples

package com.freesamplecode.java.io;

import java.io.File;

public class MoveFileDemo {
 public static void main(String[] args){
  
  String fileName = "test.txt";
  
  //source directory
  File sourceDir = new File("D:/temp/sourcedir/"+fileName);
  
  //destination directory
  File destDir = new File("D:/temp/destdir/"+fileName);
  
  if(sourceDir.renameTo(destDir)){
   System.out.println("Move File operation is successfully...");
  }else{
   System.out.println("Failed to execute move file operation, please try again...");
  }
 }
}

Output

Move File operation is successfully...

Screenshot

before move file

after move file

Java I/O Examples : How To Write An Object To File

Intro

This examples will demonstrates how to write a Java object into file using serialization method. To use serialization method, your Java class have to implement the Serializable interface.

Examples

Employee.java

public class Employee implements Serializable{
 /**
  * 
  */
 private static final long serialVersionUID = 8836890329708390627L;
 
 private long id;
 private String name;
 private String sex;
 private String placeOfBirth;
 private Date dateOfBirth;
 
 public long getId() {
  return id;
 }
 
 public void setId(long id) {
  this.id = id;
 }
 
 public String getName() {
  return name;
 }
 
 public void setName(String name) {
  this.name = name;
 }
 
 public String getSex() {
  return sex;
 }
 
 public void setSex(String sex) {
  this.sex = sex;
 }
 
 public String getPlaceOfBirth() {
  return placeOfBirth;
 }
 
 public void setPlaceOfBirth(String placeOfBirth) {
  this.placeOfBirth = placeOfBirth;
 }
 
 public Date getDateOfBirth() {
  return dateOfBirth;
 }
 
 public void setDateOfBirth(Date dateOfBirth) {
  this.dateOfBirth = dateOfBirth;
 }
 
}

WriteObjectToFileDemo.java

public class WriteObjectToFileDemo {
 public static void main(String[] args){
  //create an Employee object
  Employee employee = new Employee();
  employee.setId(879829);
  employee.setName("Nursalim");
  employee.setPlaceOfBirth("Brebes");
  employee.setDateOfBirth(new Date());
  employee.setSex("M");
  
  try {
   FileOutputStream fos = new FileOutputStream("c:/TEMP/employee.ser");
   
   ObjectOutputStream oos = new ObjectOutputStream(fos);
   oos.writeObject(employee);
   oos.close();
   
   System.out.println("Done!, Successfully write object to file...");
  } catch (FileNotFoundException e) {
   System.err.println("File not found");
   e.printStackTrace();
  } catch (IOException e) {
   System.err.println("Error encountered...");
   e.printStackTrace();
  }
  
 }
}

Output

Done!, Successfully write object to file...

Screenshot

Java I/O Examples : How To Read An Object From File

Intro

This examples will demonstrates how to read a Java object from file which means deserialization.

Examples

Employee.java

package com.freesamplecode.java.io;

import java.io.Serializable;
import java.util.Date;

public class Employee implements Serializable{
 /**
  * 
  */
 private static final long serialVersionUID = 8836890329708390627L;
 
 private long id;
 private String name;
 private String sex;
 private String placeOfBirth;
 private Date dateOfBirth;
 
 public long getId() {
  return id;
 }
 
 public void setId(long id) {
  this.id = id;
 }
 
 public String getName() {
  return name;
 }
 
 public void setName(String name) {
  this.name = name;
 }
 
 public String getSex() {
  return sex;
 }
 
 public void setSex(String sex) {
  this.sex = sex;
 }
 
 public String getPlaceOfBirth() {
  return placeOfBirth;
 }
 
 public void setPlaceOfBirth(String placeOfBirth) {
  this.placeOfBirth = placeOfBirth;
 }
 
 public Date getDateOfBirth() {
  return dateOfBirth;
 }
 
 public void setDateOfBirth(Date dateOfBirth) {
  this.dateOfBirth = dateOfBirth;
 }
 
}

ReadObjectFromFileDemo.java

public class ReadObjectFromFileDemo {
 public static void main(String[] args){
  try {
   FileInputStream fis = new FileInputStream("c:/TEMP/employee.ser");
   ObjectInputStream ois = new ObjectInputStream(fis);
   Employee employee = (Employee) ois.readObject();
   
   System.out.println("Read Employee data...");
   System.out.println("ID : " +employee.getId());
   System.out.println("Name : " +employee.getName());
   System.out.println("Place of Birth : " +employee.getPlaceOfBirth());
   System.out.println("Date of Birth : " +employee.getDateOfBirth());
   System.out.println("Gender : " +employee.getSex());
   
   ois.close();
  } catch (FileNotFoundException e) {
   System.err.println("File not found");
   e.printStackTrace();
  } catch (IOException e) {
   System.err.println("Error when accessing file");
   e.printStackTrace();
  } catch (ClassNotFoundException e) {
   e.printStackTrace();
  }
 }
}

Output

Read Employee data...
ID : 879829
Name : Nursalim
Place of Birth : Brebes
Date of Birth : Tue Mar 29 15:32:25 ICT 2016
Gender : M

Screenshot

Java I/O Examples : How To Get Temporary File Path

Intro

This examples will demonstrates how to get or display temporary file path in your operating system (os).

Examples

package com.freesamplecode.java.io;

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

public class GetTemporaryFilePathDemo {
 public static void main(String[] args){
  try {
   
   //step 1. create a temporary file
   File file = File.createTempFile("tempfile", ".tmp");
   
   //step 2. get absolute path
   String absolutePath = file.getAbsolutePath();
   
   //step 3. get temporary file path
   String temporaryFilePath = absolutePath.substring(0, absolutePath.lastIndexOf(File.separator));
   
   //step 4. print to console
   System.out.println("Absolute path : "+absolutePath);
   System.out.println("Temporary File path : "+temporaryFilePath);
   
  } catch (IOException e) {
   System.err.println("Error when creating a file..");
   e.printStackTrace();
  }
  
 }
}

Output

Absolute path : C:\Users\Dev\AppData\Local\Temp\tempfile3944253553416804097.tmp
Temporary File path : C:\Users\Dev\AppData\Local\Temp

Screenshot

Java I/O Examples : How To Read A Text File Line By Line

Intro

This examples will demonstrates how to read a text file line by line. To get this, you can use readLine() method in the BufferedReader class.

Examples

package com.freesamplecode.java.io;

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;

public class ReadFileByLineDemo {
 public static void main(String[] args){
  
  String strLine = "";
  String fileName = "D:/temp/test/file_test.txt";
  try {
   
   BufferedReader br = new BufferedReader(new FileReader(fileName));
   while((strLine = br.readLine()) != null){
    System.out.println(strLine);
   }
  } catch (FileNotFoundException e) {
   System.err.print("Unable to find file :"+fileName);
   e.printStackTrace();
  } catch (IOException e) {
   System.err.print("Error encountered when accessing file "+fileName);
   e.printStackTrace();
  }
  
 }
}

Output

Hello,
Welcome to http://free-samplecode.blogspot.com
May this website useful for you.

Thanks,

Admin

Screenshoot

Java I/O Examples : How To Set File Permissions

Intro

This examples will demonstrates how to set file permissions using Java program. To set file permissions, you can use the following methods, are File.setExecutable(), File.setReadable(), and File.setWritable() methods.

Examples

package com.freesamplecode.java.io;

import java.io.File;

public class SetFilePermissionDemo {
 public static void main(String[] args){
  File file = new File("D:/temp/test.sh");
  System.out.println("Before set permission...");
  System.out.println("Can execute? : "+file.canExecute());
  System.out.println("Can Write? : "+file.canWrite());
  System.out.println("Can Read? : "+file.canRead());
  
  file.setExecutable(true);
  file.setWritable(false);
  file.setReadable(true);
  
  System.out.println("\n After set permission....");
  System.out.println("Can execute? : "+file.canExecute());
  System.out.println("Can Write? : "+file.canWrite());
  System.out.println("Can Read? : "+file.canRead());
 }
}

Output

Before set permission...
Can execute? : true
Can Write? : false
Can Read? : true

After set permission....
Can execute? : true
Can Write? : false
Can Read? : true

Screenshot

Java IO Examples : How To Determine File Or Directory In Java

Intro

This examples will demonstrates how to determine file or directory using Java program. To determine object of File is directory or not, you can use File.isFile() method. This method will return a boolean value. Return true if object is a file, otherwise object is a directory.

Examples

package com.freesamplecode.java.io;

import java.io.File;

public class DetermineFileOrDirectoryDemo {
 public static void main(String[] args){
  File file = new File("D:/temp");
  if(file.isFile()){
   System.out.println(file.getAbsolutePath() + " is a file");
  }else{
   System.out.println(file.getAbsolutePath() + " is a directory");
  }
 }
}

Output

D:\temp is a directory

Screenshot