checkfile2.java

《A first book of java》by Gary J.Bronson 北大出版社

import java.io.*;
public class CheckFile2
{
  public static void main(String[] args)
    throws java.io.IOException
  {

    String fileName = "C:\\jdk\\prices.dat";
    String nextName = "backup.dat";

    File inFile = new File(fileName);      
    File newName = new File(nextName);   

    if (inFile.exists())
    {
      System.out.println("The file " + fileName + " exists");

        // check the type of file
      if (inFile.isDirectory())
        System.out.println("  This is a directory");
      else if (inFile.isFile())
        System.out.println("  This is a regular file");
      
        // check if file is readable
      if (inFile.canRead())
        System.out.println("  The file can be read");
      else
        System.out.println("  The file is not readable");
      
        // check if file is writable
      if (inFile.canWrite())
	System.out.println("  The file can be written to");	
      else
        System.out.println("  The file is not writeable");
  
	// report the file's length
      System.out.println("The file length is " + inFile.length() + " bytes.");
    
       // report the file's directory path
     System.out.println("The pathname of this file's parent is " + inFile.getParent());

       // rename the file
    inFile.renameTo(newName);
    System.out.println("The file has been renamed " + newName); 
    System.out.println("The full pathname for this file is " + newName.getAbsolutePath());  
  }
    else
     System.out.println("The file " + fileName + " does not exist.");
  }
}