How to read file in Java using Scanner Example - text files (original) (raw)

Reading a file with Scanner

From Java 5 onwards java.util.Scanner class can be used to read file in Java. Earlier we have seen examples of reading file in Java using FileInputStream and reading file line by line using BufferedInputStream and in this Java tutorial, we will See How can we use Scanner to read files in Java. Scanner is a utility class in java.util package and provides several convenient methods to read int, long, String, double etc from a source which can be an InputStream, a file, or a String itself.

As noted on How to get input from User, Scanner is also an easy way to read user input using System.in (InputStream) as the source. The main advantage of using Scanner for reading files is that it allows you to change delimiter using the useDelimiter() method, So you can use any other delimiter like comma, pipe instead of white space.

How to Read File in Java - Scanner Example

In this Java program, we have used java.util.Scanner to read file line by line in Java. We have first created a File instance to represent a text file in Java and then we passed this File instance to java.util.Scanner for scanning.

The scanner provides methods like hasNextLine() and readNextLine() which can be used to read file line by line. It's advised to check for next line before reading next the line to avoid NoSuchElementException in Java.

Here is the complete code example of using Scanner to read text files in Java :

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;

/**
*
* Java program to read files using Scanner class in Java.
* java.util.Scanner is added on Java 5 and offers a convenient method to read data
*
* @author
*/
public classScannerExample {

public static voidmain(String args[]) throws FileNotFoundException {

//creating File instance to reference text file in Java
File text = new File("C:/temp/test.txt");

//Creating Scanner instance to read File in Java
Scanner scnr = new Scanner(text);

//Reading each line of the file using Scanner class
intlineNumber = 1;
while(scnr.hasNextLine()){
String line = scnr.nextLine();
System.out.println("line "+ lineNumber + " :" + line);
lineNumber++;
}

}

}

Output:
line 1 :--------------------- START------
-----------------------------------------------
line 2 :Java provides several way to read files.
line 3:You can read file using Scanner, FileReader,
FileInputStreamand BufferedReader.
line 4:This Java program shows How to read file using java.util.Scanner class.
line 5:--------------------- END-----------------------
---------------------------------

This is the content of test.txt file exception line numbers. You see it doesn't require much coding to read file in Java using Scanner. You just need to create an instance of Scanner and you are ready to read file.

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