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, or the platform’s default charset may be accepted.
Declaration :
public class InputStreamReader extends Reader
Constructors :
- InputStreamReader(InputStream in_strm) : Creates an InputStreamReader that uses the default charset.
- InputStreamReader(InputStream in_strm, Charset cs) : creates an InputStreamReader that uses the given charset.
- InputStreamReader(InputStream in_strm, CharsetDecoder dec) : Creates an InputStreamReader that uses the given charset decoder.
- InputStreamReader(InputStream in_strm, String charsetName) : Creates an InputStreamReader that uses the named charset
Methods:
- ready() : java.io.InputStreamReader.ready() tells whether the Character stream is ready to be read or not. An InputStreamReader is ready if its input buffer is not empty, or if bytes are available to be read from the underlying byte stream.
Syntax :public boolean ready() Returns : True : if the Character stream is ready to be read False : if the Character stream is not ready to be read
- close() : java.io.InputStreamReader.close() closes InputStreamReader and releases all the Streams associated with it. Once the stream has been closed, further read(), ready(), mark(), reset(), or skip() invocations will throw an IOException.
Syntax :
public void close() Returns : No value is returned
Implementation of ready() and close() method :
// Java program illustrating ready() and close() method
import
java.io.*;
public
class
NewClass
{
public
static
void
main(String[] args)
{
try
{
// initializing FileInputStream
FileInputStream geek =
new
FileInputStream(
"ABC.txt"
);
// Initializing InputStreamReader object
InputStreamReader in_strm =
new
InputStreamReader(geek);
int
t;
while
((t=in_strm.read())!= -
1
)
{
// convert the integer tue to character
char
r = (
char
)t;
System.out.println(
"Character : "
+r);
// check if the stream in_strm ready
boolean
b = in_strm.ready();
// Use of ready() methods
System.out.println(
"Ready? : "
+b);
}
// Use of close() method to Close InputStreamReader
in_strm.close();
// Closing FileInputStream
geek.close();
}
catch
(FileNotFoundException fnfe)
{
System.out.println(
"NO Such File Exists"
);
}
catch
(IOException excpt)
{
System.out.println(
"IOException occured"
);
}
}
}
Note :
All the programs in this article won’t run on online IDE as no ‘ABC’ file exists. You can check this code on Java compiler on your system.
To check this code, create a file ‘ABC’ on your system.
‘ABC’ file contains :
Geeks
For
Geeks
Output :Character : G Ready? : true Character : e Ready? : true Character : e Ready? : true Character : k Ready? : true Character : s Ready? : true Character : Ready? : true Character : Ready? : true Character : Ready? : true Character : F Ready? : true Character : o Ready? : true Character : r Ready? : true Character : Ready? : true Character : Ready? : true Character : Ready? : true Character : G Ready? : true Character : e Ready? : true Character : e Ready? : true Character : k Ready? : true Character : s Ready? : false
- getEncoding() : java.io.InputStreamReader.getEncoding() returns the name of the character encoding being used by this stream.
Syntax :public String getEncoding() Parameters : Returns : No value is returned
Implementation of getEncoding() method :
// Java program illustrating getEncoding() method
import
java.io.*;
public
class
NewClass
{
public
static
void
main(String[] args)
{
try
{
// initializing FileInputStream
FileInputStream geek =
new
FileInputStream(
"ABC.txt"
);
// Initializing InputStreamReader object
InputStreamReader in_strm =
new
InputStreamReader(geek);
// Use of getEncoding() method
// to get the character encoding present in the stream
String encoding = in_strm.getEncoding();
System.out.println(
"Encoding used : "
+encoding);
// Closing InputStreamReader
in_strm.close();
// Closing FileInputStream
geek.close();
}
catch
(FileNotFoundException fnfe)
{
System.out.println(
"NO Such File Exists"
);
}
catch
(IOException excpt)
{
System.out.println(
"IOException occured"
);
}
}
}
Output :
Encoding used : UTF8
- read() : java.io.InputStreamReader.read() Returns single character after reading.
Syntax :public int read() Returns : Returns single character after reading or -1 if the end of the stream has been reached
Implementation :
// Java program illustrating read() method
import
java.io.*;
public
class
NewClass
{
public
static
void
main(String[] args)
throws
FileNotFoundException, IOException
{
// initializing FileInputStream
FileInputStream geek =
new
FileInputStream(
"ABC.txt"
);
// Initializing InputStreamReader object
InputStreamReader in_strm =
new
InputStreamReader(geek);
int
t;
String read_reslt=
""
;
// Use of read() method
while
((t = in_strm.read()) != -
1
)
{
read_reslt = read_reslt+(
char
)t;
}
// print the result read from the file
System.out.println(read_reslt);
}
}
Note :
‘ABC’ file contains :
1
Geeks
2
For
3
Geeks
Output :1 Geeks 2 For 3 Geeks
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