Reprint: Java File object manipulation

Object Java file Object manipulation

When we do a file operation, we need to know some information about the file. The file class provides some member functions to manipulate files and obtain information about some files.

1. Create a new File object

You can use the following three methods to create a new file object:

File MyFile; MyFile = new File ("ETC/MOTD");

Or

MyFile = new File ("/etc", "MOTD"); More useful if the directory or filename are variables

Or

File Mydir = new file ("/etc"); MyFile = new File (Mydir, "MOTD");

These three methods depend on how you access the file. For example, if you use only one file in an application, the first way to create a file structure is easiest. But if you open several files in the same directory, the second or third structure is better.

2, file testing and use

Once you create a file object, you can use the following member functions to obtain file-related information:

File name: String getName ()
Path: String GetPath ()
String Getabslutepath ()
String GetParent ()
Boolean Renameto (File newName)

File Tests: Boolean exists (), Boolean CanWrite (), Boolean CanRead (), Boolean Isfile (), Boolean isdirectory (), Boolean I Sabsolute ()

General file Information L long lastmodified () L long Length ()

Directory Usage L boolean mkdir () L string[] list ()

3. File Information Acquisition Example program

Here is a standalone program that displays basic information about the file, which is transmitted via command-line arguments:

Import java.io.*; Class fileinfo{
File Filetocheck;
public static void Main (String args[]) throws ioexception{
if (args.length>0) {
for (int i=0;i<args.length;i++) {
Filetocheck = new File (args[i]);
info (filetocheck);
}
}
Else
{
System.out.println ("No file given.");
}
}

public void info (File f) throws IOException {
System.out.println ("Name:" +f.getname ());
System.out.println ("Path:" =f.getpath ());
if (f.exists ()) {
System.out.println ("File exists.");
System.out.print ((F.canread ()? "and is readable": ")); System.out.print ((F.cnawrite ()? "and is writeable": ")); System.out.println ("."); System.out.println ("File is" + f.lenght () = "bytes.");} else {System.out.println ("File does not exist.");} }