File Processing - Building Java Programs: A Back to Basics Approach - page 377

8 System.out.println("exists returns " + f.exists());
9 System.out.println("canRead returns " + f.canRead());
10 System.out.println("length returns " + f.length());
11 System.out.println("getAbsolutePath returns "
12 + f.getAbsolutePath());
13 }
14 }

Notice that the program includes an import from the package java.io , because
the File class is part of that package. The term “io” (or I/O) is jargon used by com-
puter science professionals to mean “input/output.” Assuming you have stored the file
hamlet.txt in the same directory as the program, you'll get output like the follow-
ing when you run the program:

exists returns true
canRead returns true
length returns 191734
getAbsolutePath returns C:\data\hamlet.txt

The fact that we use a call on new to construct a File object can be misleading.
We aren't constructing an actual file by constructing this object. The File object is
an internal object that allows us to access files that already exist on the computer.
Later in the chapter we will see how to write a program that creates a file as output.
Table 6.2 lists some useful methods for File objects.

Reading a File with a Scanner
The Scanner class that we have been using since Chapter 3 is flexible in that
Scanner objects can be attached to many different kinds of input (see Figure 6.1).

Table 6.2 Useful Methods of File Objects

Method Description

Whether or not this file exists and can be read

canRead()

Deletes the given file

delete()

Whether or not this file exists on the system

exists()

The full path where this file is located

getAbsolutePath()

The name of this file as a String , without any path attached

getName()

Whether this file represents a directory/folder on the system

isDirectory()

Whether this file represents a file (nonfolder) on the system

isFile()

The number of characters in this file

length()

Changes this file's name to the given file's name

renameTo(file)