1. File class
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2. Objectives
On completion of this period, you would be able
to learn
• File class
• Example program using file class
• Example program to check the directory properties
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3. Recap
In the last class, we have studied about the concept of
streams
• Stream is a flow bits of information either to or
from input or output devices into or from a
program
• The various input output stream classes
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4. File Class
• It directly deals with files and the file system
• File class does not specify how information is
retrieved from or stored in files
• It describes the properties of a file itself
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5. File Class contd..
• File class defines many methods that obtain the
standard properties of a File object
• getName( ) returns the name of the file
• getParent( ) returns the name of the parent
directory
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6. File Class contd..
• exists( ) returns true if the file exists, false if it does
not
• length() : returns length of a file in bytes
• isFile() : check whether the file is normal file or
directory file
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7. // Program for finding File properties
The following program shows the use of File class
import java.io.File;
class FileDemo {
static void p(String s) {
System.out.println(s); }
public static void main(String args[]) {
File f1 = new File("/java/COPYRIGHT");
p("File Name: " + f1.getName());
p("Path: " + f1.getPath());
p("Abs Path: " + f1.getAbsolutePath());
p("Parent: " + f1.getParent());
p(f1.exists() ? "exists" : "does not exist");
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8. // Program for finding File properties
Contd . . .
p(f1.canWrite() ? "is writeable" : "is not writeable");
p(f1.canRead() ? "is readable" : "is not readable");
p("is " + (f1.isDirectory() ? "" : "not" + " a
directory"));
p(f1.isFile() ? "is normal file" : "might be a named
pipe");
p(f1.isAbsolute() ? "is absolute" : "is not absolute");
p("File last modified: " + f1.lastModified());
p("File size: " + f1.length() + " Bytes");
}
}
• When you run the program, it displays the
properties of the selected file
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9. Creating Directories
• File utility methods are mkdir( ) and mkdirs( )
• The mkdir ( ) method creates a directory, returning
true on success and false on failure
• mkdirs( ) method creates a directory for which no
path exists
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10. Other Method Related To Directory
• isDirectory (): returns Boolean can be used to
check the given file is a directory
true directory
false a file
• list() : returns the list of file names available in
given directory.
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11. // Program for checking for directory properties
import java.io.File;
class DirList {
public static void main(String args[]) {
String dirname = "/java";
File f1 = new File(dirname);
if (f1.isDirectory()) {
System.out.println("Directory of " + dirname);
String s[] = f1.list();
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12. // Program for checking for directory properties
Contd . . .
for (int i=0; i < s.length; i++) {
File f = new File(dirname + "/" + s[i]);
if (f.isDirectory()) {
System.out.println(s[i] + " is a directory");
} else {
System.out.println(s[i] + " is a file"); } }
} else {
System.out.println(dirname + " is not a directory");
}}}
• Running this program produces output based on
what was in “/java” directory
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13. Summary
• File class describes the properties of a file itself
• File defines many methods that obtain the standard
properties of a File object
• File utility methods for creating directories are
mkdir( ) and mkdirs( )
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14. Quiz
1. File class does not specify how information is
retrieved from or stored in files
A. True
B. False
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15. Quiz contd..
2. Which File method returns the name of the file
A. getName()
B. getParent( )
C. exists()
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16. Frequently Asked Questions
1. Write a java program to find the various
properties of a File class
2. Explain File class, methods and attributes of it
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