Java InputStreamReader | Java Tutorials | CodeMistic

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Java InputStreamReader

In this tutorial, we will learn about the Java InputStreamReader, its constructors and its methods with the help of an example.

An InputStreamReader is a bridge from byte streams to character streams: It reads bytes and decodes them into characters using a specified charset. The charset that it uses may be specified by name or may be given explicitly

Constructors of InputStreamReader

  • InputStreamReader(InputStream in) :Creates an InputStreamReader that uses the default charset.
  • InputStreamReader(InputStream in, Charset cs) :Creates an InputStreamReader that uses the given charset.
  • InputStreamReader(InputStream in, CharsetDecoder dec) :Creates an InputStreamReader that uses the given charset decoder.
  • InputStreamReader(InputStream in, String charsetName) :Creates an InputStreamReader that uses the named charset.

Methods

MethodsDesciption
void close()Closes the stream and releases any system resources associated with it.
String getEncoding()Returns the name of the character encoding being used by this stream.
int read()Reads a single character.
int read(char[] cbuf, int offset, int length)Reads characters into a portion of an array.
boolean ready()Tells whether this stream is ready to be read.

Examples :

Suppose we have a file named input.txt with the following content.


This file consists of a single line.


import java.io.InputStreamReader;
import java.io.FileInputStream;

class Codemistic 
{
  	public static void main(String[] args) 
	{

    		// Creates an array of character
    		char[] array = new char[100];

    		try 
		{
      			// Creates a FileInputStream
      			FileInputStream file = new FileInputStream("input.txt");

      			// Creates an InputStreamReader
      			InputStreamReader input1 = new InputStreamReader(file);

      			// Reads characters from the file
      			input.read(array);
      			System.out.println("Data in the stream:");
      			System.out.println(array);

      			// Creates an InputStreamReader specifying the encoding
      			InputStreamReader input2 = new InputStreamReader(file, Charset.forName("UTF8"));

      			// Returns the character encoding of the input stream
      			System.out.println("Character encoding of input1: " + input1.getEncoding());
      			System.out.println("Character encoding of input2: " + input2.getEncoding());

      			// Closes the reader
      			input1.close();
      			input2.close();
    		}
		catch(Exception e) 
		{
      			e.getStackTrace();
    		}
  	}
}


Output :

Data in the stream:
This file consists of a single line.
The character encoding of input1: Cp1252
The character encoding of input2: UTF8

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