Java How to Program Fourth Edition - DCC

962 Files and Streams Chapter 16
of that file without warning. If a program using a File determines that a file already exists,
the program can warn that the user is about to discard the original file’s contents.
Good Programming Practice 16.2
Use a File object to determine whether a file exists before opening the file with a File-
OutputStream object. 16.2
Class File provides three constructors. The constructor
public File( String name )
stores the String argument name in the object. The name can contain path information
as well as a file or directory name. A file or directory’s path specifies the location of the file
or directory on disk. The path includes some or all of the directories leading to the file or
directory. An absolute path contains all the directories, starting with the root directory that
lead to a specific file or directory. Every file or directory on a particular disk drive has the
same root directory in its path. A relative path contains a subset of the directories leading
to a specific file or directory. Relative paths normally start from the directory in which the
application began executing.
The constructor
public File( String pathToName, String name )
uses argument pathToName (an absolute or relative path) to locate the file or directory
specified by name.
The constructor
public File( File directory, String name )
uses an existing File object directory (an absolute or relative path) to locate the file
or directory specified by name.
Figure 16.21 discusses some common File methods. See the Java API for other
File methods.
Method Description
boolean canRead() Returns true if a file is readable; false otherwise.
boolean canWrite() Returns true if a file is writable; false otherwise.
boolean exists() Returns true if the name specified as the argument to the
File constructor is a file or directory in the specified path;
false otherwise.
boolean isFile() Returns true if the name specified as the argument to the
File constructor is a file; false otherwise.
boolean isDirectory() Returns true if the name specified as the argument to the
File constructor is a directory; false otherwise.
boolean isAbsolute() Returns true if the arguments specified to the File constructor
indicate an absolute path to a file or directory;
false otherwise.
Fig. Fig. 16.21 16.21 Some commonly used File methods (part 1 of 2).