18 - Not the Books Approach CS133 Developing Programming...

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CS133: Developing
Programming Principles
Lecture 18
Text Files
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CS 133 Course Notes Lecture 18, Slide 2
Not the Book’s Approach
We’re doing things a little differently than
the approach in the text.

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CS 133 Course Notes Lecture 18, Slide 3
Text files
A text file contains a number of lines, each
consisting of a sequence of characters.
To: Carrie
From: Charlie
The quick brown
fox jumped over
the lazy dog.
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CS 133 Course Notes Lecture 18, Slide 4
Reading a Text File
1. Open the file, using a name known to the
operating system:
C:\My Stuff\CS133\Junk\test.txt
/u/charlie/Courses/CS133/test.txt
2. Read and process each line of text.
3. Close the file.

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CS 133 Course Notes Lecture 18, Slide 5
Opening the File
import java.io.*;
import java.util.*;
FileReader in
= new FileReader( filename );
Scanner myScanner
= new Scanner(in);
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CS 133 Course Notes Lecture 18, Slide 6
Class FileReader
FileReader is a subclass of
InputStream and can be used to create
a Scanner .
FileReader in
= new FileReader("C:\\test.txt");
Throws FileNotFoundException if the
file does not exist or can’t be opened.

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CS 133 Course Notes Lecture 18, Slide 7
Reading and Printing a File
try {
FileReader in
= new FileReader("C:\\test.txt");
Scanner scanner = new Scanner(in);
while (scanner.hasNext()) {
System.out.println(scanner.nextLine());