Java 7 for Absolute Beginners

CHAPTER 8 ■ WRITING AND READING FILES

Reading a File's Content

Before we can get much further, we first need a file that contains some content. So, let's set up a test

case. Copy the content from Listing 8-12 (a few lines from Shakespeare's play, Hamlet) into a text file

called Hamlet.txt and put the file in your C:\test directory.

Listing 8-12. Original contents of Hamlet.txt

To sleep: perchance to dream: ay, there's the rub;

For in that sleep of death what dreams may come

When we have shuffled off this mortal coil,

Must give us pause: there's the respect

That makes calamity of so long life

(Feel free to use your own favorite bit of content if you don't like mine. For our purposes right now,

all we need is some text.)

Now that we have a file with some content, we can read that content into memory with a program.

To read a file's content, a Java developer generally reaches for a FileInputStream object. Listing 8-13

shows a simple program to read a file and repeat the contents in the console:

Listing 8-13. Putting hamlet.txt in the console.

package com.apress.java7forabsolutebeginners.examples;

import java.io.File;

import java.io.FileInputStream;

import java.io.FileNotFoundException;

import java.io.IOException;

public class ReadFile {

public static void main(String[] args) {

// Specify the file

String fileName = "C:" + File.separator + "test"

+ File.separator + "Hamlet.txt";

File hamletFile = new File(fileName);

// Set up a byte array to hold the file's content

byte[] content = new byte[0];

try {

// Create an input stream for the file

FileInputStream hamletInputStream = new FileInputStream(hamletFile);

// Figure out how much content the file has

int bytesAvailable = hamletInputStream.available();

// Set the content array to the length of the content

content = new byte[bytesAvailable];

// Load the file's content into our byte array

hamletInputStream.read(content);

// Close the stream

hamletInputStream.close();

} catch (FileNotFoundException fnfe) {

System.out.println("Couldn't find a file called " + fileName);