How To Read A Text File Inwards Coffee - Bufferedreader Example

There are multiple ways to read a file inwards Java e.g. y'all tin usage a Scanner equally nosotros accept seen inwards the last example, or y'all tin usage the BufferedReader class. The wages of using a BufferedReader to read a text file is speed. It allows faster reading because of internal buffering provided past times BufferedReader. Other Reader classes e.g. FileReader access the file or disk everytime y'all telephone telephone the read() method but BufferedReader keeps 8KB worth of information inwards its internal buffer which y'all tin read it without accessing file multiple times. It's loaded when y'all access the file start fourth dimension for a subsequent read. The BufferedReader shape is too a expert event of Decorator blueprint pattern because it decorates existing readers e.g. FileReader to furnish buffering, remember, the reading from file functionality nonetheless comes from the FileReader class.

One to a greater extent than wages of using the BufferedReader for reading a text file is its powerfulness to read file trouble past times line. It provides a readLine() method which tin live used to read a text file trouble past times line inwards Java.


The java.io.BufferedReader shape provides iv versions of the read() method to read information from a text file

read() - to read a unmarried character, this method render an int, thus y'all involve to cast that to a character

read(char[] cbuf) - to read characters into an array. This method volition block until unopen to input is available, an I/O mistake occurs, or the terminate of the current is reached. This method either render let on of characters read or -1 if the terminate of file has been reached. The method comes from the Reader class.

read(CharBuffer cbuffer) - to read characters into a CharBuffer, this is similar to the previous method except that it reads characters into a CharBuffer object instead of the array. This method too returns a amount let on of characters read or -1 if the terminate of file has been reached. This method too belongs to java.io.Reader class.



read(char[] cbuf, int off, int len) - to read characters into an array but gives y'all command where to shop the characters read from a file. You tin specify offset i.e. the indices to start together with length, how many characters to store.

readLine() - to read a Line of text. You tin usage this method to read a file trouble past times trouble inwards Java. Influenza A virus subtype H5N1 trouble is considered to live terminated past times whatever i of a trouble feed ('\n'), a railroad vehicle render ('\r'), or a railroad vehicle render followed directly past times a linefeed. This method returns a String containing the contents of the line, non including whatever line-termination characters, or nada if the terminate of the current has been reached. Many Java developer uses BufferedReader shape but for this method.

Btw, from Java 8 onwards at that topographic point are many ways to read a file trouble past times trouble inwards Java e.g. y'all tin usage Files.lines() method to acquire all lines equally Stream inwards Java together with and thus y'all cannot exclusively read them trouble past times trouble but too y'all tin too usage Stream operations e.g. map(), flatMap(), filter() etc to perform useful operations.

If y'all are non familiar alongside functional programming together with Java 8 encounter Java SE 8 for Really impatient to larn to a greater extent than nigh basics of functional programming alongside Java 8 syntax.

Java Program to read a text file using BufferedReader

Here is our sample Java programme to read a evidently text file using BufferedReader. In this program, I accept shown 2 examples of BufferedReader class, the start i reads file content into a character array together with the instant i reads the text file trouble past times line.

If y'all notice carefully, piece converting the grapheme array to String, nosotros accept correctly used the offset together with length because it mightiness live possible that the array which y'all are using for storing content, may content dingy information from the previous read, equally nosotros are non cleaning it upwards afterward every read. That's the wages of using offset together with length, y'all don't involve to clear or cook clean the array. See Core Java Volume 1 - Fundamentals to larn to a greater extent than nigh file reading inwards Java.

Java BufferedReader Example

import java.io.BufferedReader; import java.io.File; import java.io.FileNotFoundException; import java.io.FileReader; import java.io.IOException;  /*  * Java Program read a text file using BufferedReader.  * It allows y'all to read file trouble past times trouble or straight  * into a grapheme array.   */ public class BufferedReaderDemo {    public static void main(String[] args) throws Exception {     String filename = "newfile.txt";      // reading text file into array     try {       FileReader textFileReader = new FileReader(filename);       BufferedReader bufReader = new BufferedReader(textFileReader);        char[] buffer = new char[8096];        int numberOfCharsRead = bufReader.read(buffer); // read volition live from       // memory       while (numberOfCharsRead != -1) {         System.out.println(String.valueOf(buffer, 0, numberOfCharsRead));         numberOfCharsRead = textFileReader.read(buffer);       }        bufReader.close();      } catch (IOException e) {       // TODO Auto-generated select handgrip of block       e.printStackTrace();     }      // reading file trouble past times trouble using BufferedReader     try (BufferedReader br = new BufferedReader(new FileReader(filename))) {       String trouble = br.readLine();       while (line != null) {         System.out.println(line);         trouble = br.readLine();       }     } catch (IOException e) {       e.printStackTrace();     }    } }  Output [first line] hey [second line] goodbye [first line] hey [second line] bye

You tin encounter from the output that nosotros accept successfully read the text file. In the instant example, since nosotros accept used the try-with-resource construct, y'all don't involve to manually telephone telephone the close() method of BufferedReader, it volition automatically live called past times Java. The select handgrip of clause is at that topographic point to select handgrip of the IOException thrown past times the close() method.


That's all nigh how to read a text file using BufferedReader inwards Java. As I said, at that topographic point are 2 master copy reasons to usage the BufferedReader class, start the buffering it provides which makes reading efficient, together with instant the readLine() method it gives, which allows y'all to read the text file trouble past times line. If y'all running inwards Java 8, y'all tin too usage streams to lazily read the file content past times using Files.lines() method which returns a Stream of String from a text file. You tin together with thus perform operations similar map() together with filter() on file content.

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