Java I/O

The InputStreamReader Class

The most basic concrete subclass of Reader is InputStreamReader:

public class InputStreamReader extends Reader

The constructor connects a character reader to an underlying input stream:

public InputStreamReader(InputStream in)
public InputStreamReader(InputStream in, String encoding) 
 throws UnsupportedEncodingException

The first constructor uses the platform’s default encoding, as given by the system property file.encoding. The second one uses the specified encoding. For example, to attach an InputStreamReader to System.in with the default encoding (generally ISO Latin-1):

InputStreamReader isr = new InputStreamReader(System.in);

If you want to read a file encoded in Latin-5 (ASCII plus Turkish, as specified by ISO 8859-9), you might do this:

FileInputStream fin = new FileInputStream("symbol.txt");
InputStreamReader isr = new InputStreamReader(fin, "8859_9");

There’s no easy way to determine which encodings are supported, but the ones listed in Table 2.4 are supported by most VMs.

The read() methods read bytes from an underlying input stream and convert those bytes to characters according to the specified encoding:

public int read() throws IOException
public int read(char c[], int off, int length) throws IOException

The getEncoding() method returns a string containing the name of the encoding used by this reader:

public String getEncoding()

The remaining two methods just override methods from java.io.Reader but behave identically from the perspective of the programmer: ...