How to open, read, write, close file(s) in Java? Examples on move, rename and de

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Question: How can I open, read, write and close files in Java? Can I move, rename and delete file in Java? Examples? Can I filter files by file's extension?

Answer: Yes you can do all usual operations with files in Java: open, read, write, close, move, rename and delete.

You can even filter files by file's extension. All the file operations most easy to do in Java application. By default it is not for applets. If you try to open a file by applet you will get such or similar error (depends on Java version):

java.security.AccessControlException: access denied (java.io.FilePermission yourfilename read) at java.security.AccessControlContext. checkPermission(AccessControlContext.java:270) at java.security.AccessController. checkPermission(AccessController.java:401) at java.lang.SecurityManager. checkPermission(SecurityManager.java:542) at java.lang.SecurityManager. checkRead(SecurityManager.java:887)

It is possible to open files with applet but user must explicitly permit it to Security manager (you write this functionality). So if you write a program which runs locally it is easier to write an application instead of applet.

File operations are often OS dependant. You code which works on Windows can stop to work on UNIX-like OS's due to higher security. Files which are in mounted directories (look like they are here on local file system, but are far away on the other side of network) also can cause many troubles.. So be ready to test all the cases if you write your code for different OS's and file systems.

During my latest work as Java programmer I collected a lot of useful examples for files related operations. They all working well and can give you good idea how to use file operations in Java.

By the way, I have more than 1000 Java examples on other areas of Java as well. My principle is: only working Java Code Examples. Some examples require few more classes, you can find them by powerful Java Code Search - supports boolean search, exact pattern and more.

So please take a look at File related code examples below:

AudioChannelPlayer

Determine If a Filename Path is a File or a Directory

Converting Between Filename Path and a URL

Getting an Absolute Filename Path from a Relative Filename Path

Determining If Two Filename Paths Refer to the Same File

Getting the Parents of a Filename Path

Traversing a Directory

Listing the File System Roots

List the Files or Subdirectories in a Directory

Deleting a Directory

Creating a Directory

Getting and Setting the Modification Time of a File or Directory

Moving a File or Directory to Another Directory

Renaming a File or Directory

Creating a Temporary File

Getting the Size of a File

Creating a File

Determining If a File or Directory Exists

Using a Random Access File

Reading a File into a Byte Array

CLOB Example

BLOB Example

BFILE File Example

JNDI - File Systems Demo 1

Security Manager / Access Controller

Simple (Save / Load) Serialization Example

Property Files

Calculating the Checksum of a File / CRC-32

Calculating the Checksum of a File / Adler-32

Uncompressing File in GZIP Format

Compress File to GZIP Format

JAXP Example (Uses default parser - which is Crimson)

Crimson XML Parser Example (DOM)

Xerces2 XML Parser Example (DOM)

Oracle XML Parser Example (DOM)

SAX Example (Generic)

DOM Example (Generic)

Java Statement Runner

CharacterTranscoding

Compare File Dates

PrintFile -- Print a file named onthe command line

Create a file with holes in it.

A file searching class, similar to grep, which returns information about lines matched in the specified files.

Test behavior of Memory mapped buffer types.

DOMSerializer will take a DOM tree and serialize that tree.

UpdateItemServlet demonstrates how the DOM Level 2 Range module can be used for handling range within a do*****ent.

estSAXParsing is a simple class that demonstrates how JAXP can be used to work with SAX (the Simple API for XML).

ItemSearcher shows how the DOM Level 2 Traversal module can be used for searching through a do*****ent.

You can also look at examples for FileReader, FileWriter, FileDescriptor, FileFilter, FilenameFilter, FileInputStream, FileOutputStream, FileNotFoundException

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How do I compare two dates and times, date between dates, time between times and

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Question: How do I compare two dates and times, date between dates and so on.

Answer: Almost every month in my daily Java programming work I have this problem - to compare two or many dates or times.

Dates, Calendars are not an easy task to work with. Simple example: never do assume that all the days are 24 hours long. They are not. Some days are 25 and some 23 hours. Seems simple and obvious? Actually not. Most of people forget about it and get troubles twice a year

I collected more than 50 different only working Java code examples with Date class: everything from time, day, month, date, calendar to time synchronizing on computers by Java program (time servers and clients even). In the examples below you can see how this functionality can be used in different areas - applets, files, sound, beans, databases.

Sixth months ago the new section was started on this site - "Only working Java Code Examples". All the examples are grouped by Java technology (J2EE, J2SE, J2ME, etc.) and can be searched by powerful search engine of the site.

Look at all described above code examples here:

Date / Time Example
Calendar Example
Month View
Getting and Setting the Modification Time of a File or Directory
Beep / Date Example
Java Statement Runner
Trivial class to show use of Date & Calendar objects
Show dates before 1970, in JDK1.0/1.1 when Date was broken
Show some date uses
Create SimpleDateFormats from a string read from a file
DateDiff -- compute the difference between two dates
Compare Dates
An Applet to display the current time
The Date we are about to format
Read a file of reminders, run each when due using java.util.Timer
Time Server
Time Client
Time Server
UDP Time Client
Daytime Server
Dayclient and Dayserver - implement the Unix 'daytime' protocol.
Calendar Hack
Try Date Format - enter a time value and a SimpleDateFormat specification.
Last 24 (retrieves file if it's modified since ...)
Clock Label
Clock Label Test
Big Example

And more examples here-> Date and here Calendar

 

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