Programming Tutorials

BufferedReader sample program in Java

By: Charles Printer Friendly Format    

BufferedReader improves performance by buffering input. It has two constructors:

BufferedReader(Reader inputStream)
BufferedReader(Reader inputStream, int bufSize)

The first form creates a buffered character stream using a default buffer size. In the second, the size of the buffer is passed in bufSize. As is the case with the byte-oriented stream, buffering an input character stream also provides the foundation required to support moving backward in the stream within the available buffer. To support this, BufferedReader implements the mark() and reset() methods, and BufferedReader.markSupported( ) returns true.

The following example reworks the BufferedInputStream example, shown earlier, so that it uses a BufferedReader character stream rather than a buffered byte stream. As before, it uses mark( ) and reset( ) methods to parse a stream for the HTML entity reference for the copyright symbol. Such a reference begins with an ampersand (&) and ends with a semicolon (;) without any intervening whitespace. The sample input has two ampersands, to show the case where the reset( ) happens and where it does not. Output is the same as that shown earlier.

// Use buffered input.
import java.io.*;
class BufferedReaderDemo {
public static void main(String args[]) throws IOException {
String s = "This is a © copyright symbol " +
"but this is &copy not.\\n";
char buf[] = new char[s.length()];
s.getChars(0, s.length(), buf, 0);
CharArrayReader in = new CharArrayReader(buf);
BufferedReader f = new BufferedReader(in);
int c;
boolean marked = false;
while ((c = f.read()) != -1) {
switch(c) {
case '&':
if (!marked) {
f.mark(32);
marked = true;
} else {
marked = false;
}
break;
case ';':
if (marked) {
marked = false;
System.out.print("(c)");
} else
System.out.print((char) c);
break;
case ' ':
if (marked) {
marked = false;
f.reset();
System.out.print("&");
} else
System.out.print((char) c);
break;
default:
if (!marked)
System.out.print((char) c);
break;
}
}
}
}

This tutorial is an extract from the "The Complete Reference Part 2 by Herbert Schildt".