1. Files – part 2
Alexandra Stefan

2. File Operations Read from file Write to file Close a file
Open for reading
Read
Process line: String.split
Write to file
Open for writing
Write
Close a file

3. Other File Operations File path Create a directory
Local, Absolute, Relative
File path separator
It depends on the operating system
Do not hardcode it. Get the one for the system you are running on.
Create a directory
Delete a file or a directory
List directories
Useful:
System, System.getProperty(…)
File:

4. File Path File path separator - Do not hardcode.
Unix: / , Windows: \ (\ as a string will be: "\\")
Get the one for the system you are running using either:
String sep = File.separator; //or:
String sep = System.getProperty("file.separator");
// sep will be "\\" or "/"
Build a file path - String concatenation
String fPath = ".." + sep + "data1.txt" //fPath:..\data1.txt or ../data1.txt
String dirName = System.getProperty("user.home");
String fPath2 = dirName + sep + "datasets" + sep + "data1.txt"
// fPath2 is: C:\Users\alex\datasets\data1.txt
// Actual string "C:\\Users\\alex\\datasets\\data1.txt"
File path
Example
Description
Local
data1.txt
Looks in the current project folder.
Absolute
C:\Users\alex\courses\1310\data1.txt
Complete path name. Do not use it!
Relative:up
down
..\data1.txt
hw3\data1.txt
Move ‘up’ or ‘down’ from the current folder. USEFUL.

5. Directory and Other Create File object:
File f = new File(parentDirName, "newDir");
Create a directory: f.mkdir(), f.mkdirs()
Delete a directory: f.delete()
List content of the directory: f.list()
Other:
f.exists()
f.isDirectory(), f.isFile()
f.lastModified()
File:

6. System Properties Get them using: Examples:
System.getProperty( propertyStr );
Examples:
Line separators (for new line)
File name separators,
User’s working and home directories
See: