1. CharacterStream Classes
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2. Objectives
On completion of this period, you would be able
to learn
• CharacterStream classes
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3. Recap
In the last class, we have studied about
CharacterStream classes
• Where character stream classes deal with the
character oriented text
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4. CharArrayReader class
• Is an implementation of an input stream that
uses a character array as the source
• Is used to read an array of characters from a
memory buffers
• Constructors
• CharArrayReader(char array[ ])
• CharArrayReader(char array[ ], int start, int
numChars)
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5. Example:
// Demonstrate CharArrayReader.
import java.io.*;
public class CharArrayReaderDemo {
public static void main(String args[]) throws
IOException {
string tmp = "abcdefghijklmnopqrstuvwxyz";
int length = tmp.length();
char c[] = new char[length];
tmp.getChars(0, length, c, 0);
CharArrayReader input1 =new CharArrayReader(c);
CharArrayReader input2 = new CharArrayReader(c,
0, 5);
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6. Example: contd..
int i;
System.out.println("input1 is:");
while((i = input1.read()) != -1) {
System.out.print((char)i); }
System.out.println();
System.out.println("input2 is:");
while((i = input2.read()) != -1) {
System.out.print((char)i); }
System.out.println(); } }
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7. CharArrayWriter class
• CharArrayWriter is an implementation of an
output stream that uses an array as the
destination
• It is used for writing an array of characters to a
memory buffer
• CharArrayWriter has two constructors
• CharArrayWriter( )
• CharArrayWriter(int numChars)
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8. BufferedReader class
• BufferedReader improves performance by
buffering input
• This class is used to increase the efficiency of
reading
• It cannot directly access any source
• It has two constructors
• BufferedReader(Reader input Stream)
• BufferedReader(Reader input Stream, int bufSize)
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9. BufferedWriter class
• A Buffered Writer is a Writer that adds a
flush( ) method that can be used
• To ensure that data buffers are physically
written to the actual output stream
• Buffered Writer can increase performance by
reducing the number of times data is actually
physically written to the output stream
• Constructors
• BufferedWriter(Writer outputStream)
• BufferedWriter(Writer outputStream, int bufSize)
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10. Example:2
// Program for word count for a given input file
import java.io.*;
class WordCount {
public static int words = 0;
public static int lines = 0;
public static int chars = 0;
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11. Example:2 contd..
public static void wc (InputStreamReader isr)
throws IOException {
int c = 0;
boolean lastWhite = true;
String whiteSpace = " tnr";
while ((c = isr.read()) != -1) {
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12. Example:2 contd..
// count characters
chars++;
if (c == 'n') {
// Count lines
lines++; }
// Count words by detecting the start of a word
int index = whiteSpace.indexOf(c);
}
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13. Example:2 contd..
if(index == -1) {
if(lastWhite == true) {
++words; }
lastWhite = false; }
else {
lastWhite = true; } }
if(chars != 0) {
++lines; } }
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14. Example:2 contd..
public static void main(String args[]) {
FileReader fr;
try {
if (args.length == 0) { // We're working with stdin
wc(new InputStreamReader(System.in)); }
else { // We're working with a list of files
for (int i = 0; i < args.length; i++) {
fr = new FileReader(args[i]);
wc(fr); } } }
catch (IOException e) {
return; }
System.out.println(lines + " " + words + " " +
chars); } }
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15. Summary
• CharacterArrayReader an implementation of an
input stream that uses a character array as the
source and
• Used to read an array of characters from a
memory buffers
• CharArrayWriter is used for writing an array of
characters to a memory buffer
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16. Summary contd..
• BufferedReader improves performance by
buffering input
• BufferWriter ensures that data buffers are
physically written to the actual output stream
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17. Quiz
1. Which stream is used to read an array of
characters from a memory buffers
1. CharArrayReader
2. CharArrayWriter
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18. Quiz contd..
2. Which stream is used for writing an array of
characters to a memory buffer
1. CharArrayWriter
2. CharArrayReader
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19. Frequently Asked Questions
• Write about CharArrayReader, CharArrayWriter
• Write about BufferedReader, and BufferedWriter
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