Java File Class Tutorial and Example

The File class of java.io package, is an abstract representation of file and directory structures.  If you are looking for class to handle file and directory operations, the File class suits this requirements. Let’s take a look a more detailed functionality of File class.

In real life applications, most of the user interfaces and operating systems use system-dependent pathname string with regards to naming files and directories. To illustrate further a fully qualified pathname in unix looks like ‘/apps/java/test.txt’ while in windows is somewhat similar to ‘D:javatest.txt’. Did you notice the difference? The File class offer a system independent view of hierarchical pathnames.

The conversion of a pathname string to or from an abstract pathname is inherently system-dependent. When an abstract pathname is converted into a pathname string, each name is separated from the next by a single copy of the default separator character. The default name-separator character is defined by the system property file.separator, and is made available in the public static fields separator and separatorChar of this class. When a pathname string is converted into an abstract pathname, the names within it may be separated by the default name-separator character or by any other name-separator character that is supported by the underlying system.

A pathname, whether abstract or in string form, may be either absolute or relative. An absolute pathname is complete in that no other information is required in order to locate the file that it denotes. A relative pathname, in contrast, must be interpreted in terms of information taken from some other pathname. By default the classes in the java.io package always resolve relative pathnames against the current user directory. This directory is named by the system property user.dir, and is typically the directory in which the Java virtual machine was invoked.

In getting the parent of an abstract pathname, the getParent() method is available. Each directory’s absolute pathname is an ancestor of any File object with an absolute abstract pathname which begins with the directory’s absolute pathname. For example, the directory denoted by the abstract pathname “/usr” is an ancestor of the directory denoted by the pathname “/usr/local/bin”.

public class File
extends Object
implements Serializable, Comparable

StringTokenizer Class is available since Java 1.0

The File class as part of the java.io package is one of the classes of the java api that is widely used because it provides mechanism in accessing Files. It has methods to create, delete and modify file attributes. This is an abstract representation of a physical file on the system. This class is practically the most important method of java as most of the Reader classes such as Scanner, FileReader are all relying to File class to represent a physical file. For example

Scanner s = new Scanner(new File(“/tmp/test.xt”));

The following are the detailed list of File methods and descriptions. We have also provided links to examples of each method on the list.