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This page discusses - Working With File,Java Input,Java Input Output,Java Inputstream,Java io Tutorial,Java io package,Java io example

Working With File

     

In the previous chapter, we learned how to work with the streams. which provide a simple model for reading and writing data. However, streams don't support all the operations that are common with a disk file. In lesson, we will learn how to work with a file using the non-stream file I/O.

The File class is used to deals with most of the machine dependent files in a machine-independent manner i.e. it easier to write platform-independent code that examines and manipulates files using the File class. This class is available in the java.lang package. The java.io.File is the central class that works with files and directories. The instance of this class represents the name of a file or directory on the host file system. 

When a File object is created, the system doesn't check to the existence of a corresponding file/directory. If the file exist, a program can examine its attributes and perform various operations on the file, such as renaming it, deleting it, reading from or writing to it.

The constructors of the File class are shown in the table:

 Constructor  Description
 File(path)  Create File object for default directory (usually where program is located).
 File(dirpath,fname)  Create File object for directory path given as string.
 File(dir, fname)  Create File object for directory.

Thus the statement can be written as:

File f = new File("<filename>");

The methods that are used with the file object to get the attribute of a corresponding file shown in the table.

 Method  Description
 f.exists()  Returns true if file exists.
 f.isFile()  Returns true if this is a normal file.
 f.isDirectory()  true if "f" is a directory.
 f.getName()  Returns name of the file or directory.
 f.isHidden()  Returns true if file is hidden.
 f.lastModified()  Returns time of last modification.
 f.length()  Returns number of bytes in file.
 f.getPath()  path name.
 f.delete()  Deletes the file.
 f.renameTo(f2)  Renames f to File f2. Returns true if successful.
 f.createNewFile()  Creates a file and may throw IOException. 

Lets see an example that checks the existence of  a specified file.

import java.io.*;

public class CreateFile1{
  public static void main(String[] argsthrows IOException{
  File f;
  f=new File("myfile.txt");
  if(!f.exists()){
  f.createNewFile();
  System.out.println("New file \"myfile.txt\" has been created 
  to the current directory"
);
  }
  }
}

First, this program checks, the specified file "myfile.txt" is exist or not. if it does not exist then a new file is created with same name to the current location. 

Output of the Program

C:\nisha>javac CreateFile1.java

C:\nisha>java CreateFile1
New file "myfile.txt" has been created to the current directory

C:\nisha>

If you try to run this program again then after checking the existence of the file, it will not be created and you will see a message as shown in the output.

C:\nisha>javac CreateFile1.java

C:\nisha>java CreateFile1
The specified file is already exist


C:\nisha>

Download this Program

 

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Posted on: April 17, 2011

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Comments:1
MEENA
August 13, 2011
java package listing program

nothing
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