In this example we will show how to open and read a file in Java. There are many ways to do this, but we will show two of them. For this example, we will read the contents of a text file named “test_file.txt”.
1. Read a file using BufferedReader
This is the most commonly-used method in order to read a file in Java. BufferedReader reads text from a character-input stream, buffering the characters for the more efficient reading of characters, arrays, and lines.
Create a java class named ReadFileBufferedReader.java with the following code:
ReadFileBufferedReader.java
package com.javacodegeeks.javaio.readfile;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
public class ReadFileBufferedReader {
private static String filepath = "/home/konstantina/test_file.txt";
public static void main(String[] args) {
BufferedReader br;
String curline;
try {
br = new BufferedReader(new FileReader(filepath));
while ((curline = br.readLine()) != null) {
System.out.println(curline);
}
br.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
In this case, we used the class FileReader along with BufferedReader. FileReader needs the file’s name and path so as to open the file. The BufferedReader class provides a method named readLine() so as to read each line of the file. There is a while loop which is executed till readLine() reaches the end of the file.
If we run the above code, we will see the contents of the file “test_file.txt”.
- Output:
This is a test file.
Read file example
provided by
examples.javacodegeeks.com
2. Read a file using FileInputStream
This is another way of reading a file. FileInputStream reads streams of raw bytes from a file. So, we need to convert those bytes to characters in order to display the contents of the file to the screen.
Create a java class named ReadFileInputStream.java with the following code:
ReadFileInputStream.java
package com.javacodegeeks.javaio.readfile;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
public class ReadFileInputStream {
private static String filepath = "/home/konstantina/test_file.txt";
public static void main(String[] args) {
try {
File file = new File(filepath);
FileInputStream in = new FileInputStream(file);
System.out.println("Total bytes to read from file : "
+ in.available());
int i;
StringBuffer buf = new StringBuffer("");
while ((i = in.read()) != -1) {
// convert byte to char and append to StringBuffer
buf.append((char) i);
}
in.close();
System.out.println("File contents :");
System.out.println(buf);
} catch (IOException e) {
e.printStackTrace();
}
}
}
If we run the above code, we will have the following results:
- Output:
Total bytes to read from file : 78
File contents :
This is a test file.
Read file example
provided by
examples.javacodegeeks.com
3. Download the source code
You can download the source code of this example from here: ReadFileExample.zip
