Java Reader Class

In this tutorial, we will understand Java Reader, its subclasses, and its methods through an example.

The Reader class in the java.io package is an abstract superclass that represents character streams.

Since Reader is an abstract class, it does not work by itself. However, its subclasses can be used to read data.

Reader subclasses

To use the functions of Reader, we can use its subclasses. Some of them are:

• BufferedReader

• InputStreamReader

• FileReader

• StringReader

In the next tutorial, we will learn about all these subclasses.

Create Reader

To create a Reader, we must first import the java.io.Reader package. After importing the package, we can create a Reader.

//　Create Reader
Reader input = new FileReader();

Here, we have created a Reader using the FileReader class. This is because Reader is an abstract class. Therefore, we cannot create an object of Reader.

Note：We can also create ReaderReader from other subclasses.

Reader methods

The Reader class provides methods implemented differently by its subclasses. Here are some commonly used methods:

• ready(); - Check if the Reader is ready to read

• read(char[] array)　 - Read characters from the stream and store them in the specified array

• read(char[] array, int start, int length)- Read a number of characters equal to length from the stream and store them starting from start in the specified array

• mark(); - Mark the position of the read data in the stream

• reset(); - Reset the stream. If the stream has been marked, then try to mark it again to reposition. If the stream has not been marked, then try to reset it to an appropriate specific stream's methods, such as by relocating it to its starting point.

• skip(); -Discard a specified number of characters from the stream

Example: Using FileReader's Reader

This is how we implement the Reader method using the FileReader class.

Assuming we have a file namedinput.txtThe file contains the following content.

This is a line of text inside the file.

Let's try to read this file using FileReader (a subclass of Reader).

import java.io.Reader;
import java.io.FileReader;
class Main {
　　　　public static void main(String[] args) {
　　　　　　　　//　Create a character array
　　　　　　　　char[] array = new char[100];
　　　　　　　　try {
　　　　　　　　　　　　//Create a Reader using FileReader
　　　　　　　　　　　　Reader input = new FileReader("input.txt");
　　　　　　　　　　　　//Check if the Reader is ready　
　　　　　　　　　　　　System.out.println("Is there data in the stream?  ");　+　input.ready());
　　　　　　　　　　　　//Read a character
　　　　　　　　　　　　input.read(array);
　　　　　　　　　　　　System.out.println("The data in the stream:");
　　　　　　　　　　　　System.out.println(array);
　　　　　　　　　　　　//　Close reader
　　　　　　　　　　　　input.close();
　　　　　　　　}
　　　　　　　　catch(Exception e) {
　　　　　　　　　　　　e.getStackTrace();
　　　　　　　　}
　　　　}
}

Output Result

Is there data in the stream? true
Data in the stream:
This is a line of text inside the file.

In the above example, we used the FileReader class to create a reader. The Reader is linked to the fileinput.txtLink.

Reader input = new FileReader("input.txt");

In order toinput.txtFile reading data, we have implemented these methods.

input.read();　　　　　　　//Reading data from reader
input.close();　　　　　　//Close reader