JAVA STREAM AND FILES-II

 

STREAM AND FILES-II

Reader and Writer classes

Reader

     Reader is an abstract class that defines java's model of streaming character input. All of the methods in this class will throw an IOException on error condition.

File Reader

     The FileReader class creates a Reader that you can use to read the content of a file. its two most commonly used constructors are shown here

FileReader(Stringfile Path)

FileReader(Filefile Obj)

 

EXAMPLE:1

File name: FileReaderDemo.java

import java.io.*;

class FileReaderDemo{

       public static void main(String args[]) throws Exception {

            FileReader fr=new FileReader("FileReaderDemo.java");

             BufferedReader br=new BufferedReader(fr);

             String s;

             while((s=br.readLine()) !=null){

                      System.out.println(s);

              }

              fr.close();

       }

}

 

Output

 

 

File Writer

   FileWriter creates a writer that you can use to write to a file.its most commonly used constructors are shown here

FileWriter(Stringfile Path)

FileWriter(Stringfile Path,boolean append)

FileWriter(File fileObj)

Example : 2

// Demonstrate FileWriter.

File name: FileWriterDemo.java

import java.io.*;

class FileWriterDemo{

public static void main(String args[]) throws Exception{

 String source="Now is the time for all good men\n"+" to come to the aid of their country\n"

  +" and paid their due taxes.";

 char buffer[]=new char[source.length()];

source.getChars(0,source.length(),buffer,0);

FileWriter f1=new FileWriter("file1.txt");

for(int i=0;i<buffer.length;i+=1){

       f1.write(buffer[i]);

}

f1.close();

FileWriter f2=new FileWriter("file2.txt");

f2.write(buffer);

f2.close();

FileWriter f3=new FileWriter("file3.txt");

f3.write(buffer,buffer.length-buffer.length/4,buffer.length/4);

f3.close();

}

}

 

Output

CharArrayReader

     CharArrayReader is an implementation of an input stream that uses a character array as the source.To provide the data source:

CharArrayReader(char array[])

CharArrayReader(char array[],intstart,intnumChars)

EXAMPLE : 3

// Demonstrate CharArrayReader.

import java.io.*;

public class CharArrayReaderDemo

{

public static void main(String args[]) throws IOException

{

String temp="abcdefghijklmnopqrstuvwxyz";

int length=temp.length();

char c[]=new char[length];

temp.getChars(0,length,c,0);

CharArrayReader input1=new CharArrayReader(c);

CharArrayReader input2=new CharArrayReader(c,0,5);

 int I;

 System.out.println("inputl 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();

}

}

Output

 

CharArrayWriter

         CharArrayWriter is an implementation of an output stream that uses an array as the destination.CharArrayWriter has two constructors,shown here:

CharArrayWriter()

CharArrayWriter(int numChars)

EXAMPLE :4

File name: CharArrayWriterDemo.java

import java.io.*;

class CharArrayWriterDemo{

           public static void main(String args[]) throws IOException{

            CharArrayWriter f=new CharArrayWriter();

            String s="This should end up in the array";

            char buf[]=new char[s.length()];

             s.getChars(0,s.length(),buf,0);

             f.write(buf);

             System.out.println("Buffer as a string");

             System.out.println(f.toString());

             System.out.println("Into array");

             char c[]=f.toCharArray();

              for(int i=0;i<c.length;i++){

                          System.out.print(c[i]);

               }

               System.out.println("\nTo a FileWriter()");

               FileWriter f2=new FileWriter("test.txt");

               f.writeTo(f2);

               f2.close();

               System.out.println("Doing a reset");

               f.reset();

               for(int i=0;i<3;i++)

                f.write('X');

                System.out.println(f.toString());

}

}

Output

 

 

BufferedReader

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

BufferedReader(Reader inputStream)

BufferedReader(Reader inputStream,int bufSize)

EXAMPLE :5

File name: BRReadLines.java

import java.io.*;

class BRReadLines{

               public static void main(String args[]) throws IOException

               {

                           // create a BufferedReader using System.in

                            BufferedReader br= new BufferedReader(new  InputStreamReader(System.in));

String str;

System.out.println("Enter lines of text.");

System.out.println("Enter 'stop' to quit.");

do {

               str=br.readLine();

               System.out.println(str);

}while(!str.equals("stop"));

}

}

 

Output

 

BufferedWriter

   a BufferedWriter is an Writer that adds a flush() method that can be used to ensure that data buffers are physically written to the actual output stream. using a BufferedWriter can increase performance by reducing the number of times data is

actually physically written to the output stream

A BufferedWriter has these two constructors:

BufferedWriter(Writer outputStream)

BufferedWriter(Writer outputStream,int bufSize)

PrintWriter

   PrintWriter is essentially a character-oriented version of Print Stream . it provides the formatted output methods print() andprintln().PrintWriter has four constructors:

PrintWriter(OutputStream outputStream)

PrintWriter(OutputStream outputStream,boolean flushOnNewline) 

 PrintWriter(Writer outputStream)

 PrintWriter(Writer outputStream, boolean flushOnNewline)

 

EXAMPLE :6

//Demonstrate PrintWriter

File name: PrintWriterDemo.java

import java.io.*;

public class PrintWriterDemo{

public static void main(String args[]){

PrintWriter pw = new PrintWriter(System.out,true);

pw.println("This is a string");

int i=-7;

pw.println(i);

double d = 4.5e-7;

pw.println(d);

             }

}

Output