Java File Examples

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1. How to check if a file exists
2. How to delete a file or folder
3. How to rename a file or folder
4. How to copy a file
5. How to list files with same extensions/how to list only same type files / How to use FilenameFilter
6. How to move a file in Java

1. How to check if a file exists

package io;

import java.io.File;

public class FileExample {

 /**
  * This is to check whether a file( not folder) exists.
  */
  public static boolean isFileExist(String filePath) throws Exception {

  boolean exists = false;
  File file = null;
  try {
   file = new File(filePath);
   exists = file.isFile();
  } catch (Exception e) {
   throw new Exception("Exception thrown while checking the file!", e);
  } finally {
   if (file != null) {
    file = null;
   }
  }
  return exists;
 }
 }

2. How to delete a file or folder

package io;

import java.io.File;

public class FileExample {

 /**
  * This is to delete a file or folder.
  */
  public static void deleteFile(String filePath) throws Exception {
  File file = null;
  try {
   file = new File(filePath);
   if (file != null) {
    file.delete();
   }
  } catch (Exception e) {
   throw new Exception("Exception thrown while deleting the file!", e);
  } finally {
   if (file != null) {
    file = null;
   }
  }
 }

}

3. How to rename a file or folder

package io;

import java.io.File;

public class FileExample {

 /**
  * This is to rename a file or folder.
  */
  public static void rename(String loaction, String currentName, String newName) throws Exception {
  File currentFile = null;
  File newFile = null;
  try {
   currentFile = new File(loaction + File.separator + currentName);
   newFile = new File(loaction + File.separator + newName);
   if (currentFile != null) {
    currentFile.renameTo(newFile);
   }
  } catch (Exception e) {
   throw new Exception("Exception thrown while deleting the file!", e);
  } finally {
   if (currentFile != null || newFile != null) {
    currentFile = null;
    newFile = null;
   }
  }
 }
}

4. How to copy a file

class CopyFile {

 public static void main(String[] args) {
  try {
   CopyFile copyFile = new CopyFile();
   copyFile.copyFile("test.txt", "C:/temp/", "C:/temp/subtmp/");
   System.out.println("done");
  } catch (Exception e) {
   e.printStackTrace();
  }
 }

 public void copyFile(String fileName, String fromLocation, String toLocation) throws Exception {

  FileChannel srcChannel = null;
  FileChannel dstChannel = null;
  try {
   srcChannel = new FileInputStream(fromLocation + File.separator + fileName).getChannel();
   dstChannel = new FileOutputStream(toLocation + File.separator + fileName).getChannel();

   // Copy file contents from source to destination
   dstChannel.transferFrom(srcChannel, 0, srcChannel.size());

  } catch (Exception e) {
   throw new Exception(e.getMessage(), e);
  } finally {
   // Closing the channels
   try {
    if (srcChannel != null) {
     srcChannel.close();
    }
    if (dstChannel != null) {
     dstChannel.close();
    }
   } catch (IOException ioException) {
    throw new Exception("Exception thrown while closing the channels inside finally!", ioException);
   }
  }
 }
}

5. How to list files with same extensions/how to list only same type files / How to use FilenameFilter

package io;

import java.io.*;
import java.util.*;

public class FileExample {

 public static void main(String[] args) {
  try {
   FileExample example = new FileExample();
   example.listPDFFiles("C:/temp/subtmp/");
   System.out.println("done");
  } catch (Exception e) {
   e.printStackTrace();
  }
 }

 public void listPDFFiles(String folderPath) throws Exception {
  File file = null;
  try {
   file = new File(folderPath);
   FilenameFilter pdfFilter = new PDFFilter();
   String[] list = file.list(pdfFilter);
   for (int i = 0; i < list.length; i++) {
    System.out.println(list[i]);
   }
  } catch (Exception e) {
   throw new Exception("Exception thrown while checking the file!", e);
  } finally {
   if (file != null) {
    file = null;
   }
  }
 }

 class PDFFilter implements FilenameFilter {
  public boolean accept(File dir, String name) {
   return (name.toLowerCase().endsWith(".pdf"));
  }
 }
}

6. How to move a file in Java

package io;

import java.io.*;
import java.util.*;

public class FileExample {

 public static void main(String[] args) {
  try {
   FileExample.move("C:/temp/subtmp/newtest.txt", "C:/temp/subtmp/a/newtest.txt");
   System.out.println("done");
  } catch (Exception e) {
   e.printStackTrace();
  }
 }

 public static void move(String srcFilePath, String destFilePath) throws Exception {
  File scrFile = null;
  File destFile = null;
  try {
   scrFile = new File(srcFilePath);
   destFile = new File(destFilePath);
   if (scrFile != null) {
    scrFile.renameTo(destFile);
   }
  } catch (Exception e) {
   throw new Exception("Exception thrown while moving the file!", e);
  } finally {
   if (scrFile != null || destFile != null) {
    scrFile = null;
    destFile = null;
   }
  }
 }
}