input-output Archives

Concatenate & Buffer File in Java

Concatenate: It is possible to concatenate two or more files and save in a different file.

In java, by using SequenceInputStream class we can concatenate two or more files.

Buffer Files: In java, we can create a buffer to store temporary data that is read from & written to a stream and this process known as i/o buffer operation.

Buffer is sit between programmer and source/destination file.

Buffer can be created by using following classes:

BufferedInputClass
BufferedOutputClass

Example: write a program to concatenate two file A & B and concatenated data print on output screen.

import java.io.*;
public class FileConcat {
    public static void main(String arg[]) throws IOException {
        FileInputStream I1 = null;
        FileInputStream I2 = null;
        I1 = new FileInputStream("A.txt"); //open file A for concatenate	
        I2 = new FileInputStream("B.txt"); //open file B for concatenate
        //	declare sis to store combined file		
        SequenceInputStream sis = null;
        sis = new SequenceInputStream(I1, I2);
        // create buffer for input output	
        BufferedInputStream ibs = new BufferedInputStream(sis);
        BufferedOutputStream obs = new BufferedOutputStream(System.out);
        int c;
        while ((c = ibs.read()) != -1) // read& write till the end of buffer
        {
            obs.write((char) c);
        }
        ibs.close();
        obs.close();
        I1.close();
        I2.close();
    }
}

import java.io.*;

public class FileConcat {

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

FileInputStream I1 = null;

FileInputStream I2 = null;

I1 = new FileInputStream("A.txt"); //open file A for concatenate

I2 = new FileInputStream("B.txt"); //open file B for concatenate

// declare sis to store combined file

SequenceInputStream sis = null;

sis = new SequenceInputStream(I1, I2);

// create buffer for input output

BufferedInputStream ibs = new BufferedInputStream(sis);

BufferedOutputStream obs = new BufferedOutputStream(System.out);

int c;

while ((c = ibs.read()) != -1) // read& write till the end of buffer

{

obs.write((char) c);

}

ibs.close();

obs.close();

I1.close();

I2.close();

}

Suppose we have a File “A.txt”

Hello students I am aditya.

and File “B.txt”

Hello

Output: Hello students I am aditya. Hello

Example: Write a program to copy the content of one file to another file using buffer/BufferReader.

import java.io.*;
public class FileCopy1 {
    public static void main(String[] args) throws IOException {
        PrintWriter pw = new PrintWriter("B.txt"); // PrintWriter  for write on file  B
        BufferedReader br = new BufferedReader(new FileReader("A.txt"));
        String line = br.readLine(); // read first line from file A
        while (line != null) // loop to copy each line of A.txt to  C.txt
        {
            pw.println(line);
            line = br.readLine();
        }
        pw.flush();
        // closing resources 
        br.close();
        pw.close();
    }
}

import java.io.*;

public class FileCopy1 {

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

PrintWriter pw = new PrintWriter("B.txt"); // PrintWriter for write on file B

BufferedReader br = new BufferedReader(new FileReader("A.txt"));

String line = br.readLine(); // read first line from file A

while (line != null) // loop to copy each line of A.txt to C.txt

{

pw.println(line);

line = br.readLine();

}

pw.flush();

// closing resources

br.close();

pw.close();

}

Suppose we have a File “A.txt”

Hello students I am aditya.

Output: File “B”

Hello students I am aditya.

Note: If there is no file “B” it will be create automatically.

Example: Write a program to concatenate two file A & B and save the concatenated data on a file C.

import java.io.*;
public class FileMerge {
    public static void main(String[] args) throws IOException {
        PrintWriter pw = new PrintWriter("C.txt"); // PrintWriter  for write on C.txt

        // BufferedReader object for A.txt 
        BufferedReader br = new BufferedReader(new FileReader("A.txt"));

        String line = br.readLine(); // read first line from file A
        while (line != null) // loop to copy each line of A.txt to  C.txt
        {
            pw.println(line);
            line = br.readLine();
        }

        br = new BufferedReader(new FileReader("B.txt"));

        line = br.readLine(); // read first line from file B
        while (line != null) // loop to copy each line of B.txt to  C.txt
        {
            pw.println(line);
            line = br.readLine();
        }

        pw.flush();

        // closing resources 
        br.close();
        pw.close();
    }
}

import java.io.*;

public class FileMerge {

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

PrintWriter pw = new PrintWriter("C.txt"); // PrintWriter for write on C.txt

// BufferedReader object for A.txt

BufferedReader br = new BufferedReader(new FileReader("A.txt"));

String line = br.readLine(); // read first line from file A

while (line != null) // loop to copy each line of A.txt to C.txt

{

pw.println(line);

line = br.readLine();

}

br = new BufferedReader(new FileReader("B.txt"));

line = br.readLine(); // read first line from file B

while (line != null) // loop to copy each line of B.txt to C.txt

{

pw.println(line);

line = br.readLine();

}

pw.flush();

// closing resources

br.close();

pw.close();

}

Suppose we have a File “A.txt” and File “B.txt”

Hello students I am aditya.

Hello

Output: File “C”

Hello students I am aditya. Hello

Note: Ifthere is no file “C” it will be create automatically.

DataInputStream and DataOutputStream for primitive data

In java, basic input-output stream provides a method for reading & writing bytes or character in a file.

If we want to read-write primitive data typa (such as int , float etc.) than we can use filter classes to filter data in the original stream.

DataInputStream & DataOutputStream are two filter classes used for creating “data streams” for handling primitive data type.

1 DataInputStream Class

In java DataInputStream class is used to allow application to read primitive data from different sources.

DataInputStream is a sub type of FilterInputStream.

A. DataInputStream Constructor

Sr No	Constructor
1	DataInputStream(InputStream in) Take InputStream object to create DataInputStream

Constructor call of DataInputStream

FileInputStream i = new FileInputStream("A.txt"); //open file A for read DataInputStream I = new DataInputStream(i);

B Methods in DataInputStream

Following are the methods of DataInputStream

Sr No	Method
1	public final int read(byte[] b) throws IOException Reads number of bytes from input stream and store in buffered array b
2	public final int read(byte[] b, int off, int len) throws IOException Reads up to len bytes from input stream and store in buffered array b
3	public final boolean readBoolean() throws IOException Reads one input byte and return true if byte is non zero, else false
4	public final byte readByte() throws IOException Reads and return one input byte
5	public final char readChar() throws IOException Reads two input byte and return a char
6	public final double readDouble() throws IOException Reads eight input byte and return a double value
7	public final float readFloat() throws IOException Reads four input bytes and return a float value
8	public final void readFully(byte[] b) throws IOException Reads some bytes from input stream and store in buffer array b
9	public final int readInt() throws IOException Reads four input bytes and return a integer value
10	public final long readLong() throws IOException Reads eight input bytes and returns a long value
11	public final short readShort() throws IOException Reads one input bytes and returns a short value
12	public final int readUnsignedByte() throws IOException Reads two byte and return unsigned byte value
13	public final String readUTF() throws IOException Reads a string that has been encoded in modified utf-8 format
15	public static final String readUTF(DataInput in) throws IOException Reads from a stream that has been encoded in modified utf-8 format
16	public final int skipBytes(int n) throws IOException Makes attempt to skip n bytes of data from input stream

Example: Write a program to write & read a primitive data on a same file.

import java.io.*;
public class PrimitiveReadWrite {
    public static void main(String args[]) throws IOException {
        FileOutputStream o = new FileOutputStream("A.txt"); //Open file “A” for write
        DataOutputStream O = new DataOutputStream(o);
        //write primitive data on file A
        O.writeInt(1999);
        O.writeDouble(333.89);
        O.writeBoolean(false);
        O.writeChar('X');
        O.close();
        o.close();
        //read primitive data from file A
        FileInputStream i = new FileInputStream("A.txt"); //open file A for read
        DataInputStream I = new DataInputStream(i);
        System.out.println(I.readInt());
        System.out.println(I.readDouble());
        System.out.println(I.readBoolean());
        System.out.println(I.readChar());
        I.close();
        i.close();
    }
}

import java.io.*;

public class PrimitiveReadWrite {

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

FileOutputStream o = new FileOutputStream("A.txt"); //Open file “A” for write

DataOutputStream O = new DataOutputStream(o);

//write primitive data on file A

O.writeInt(1999);

O.writeDouble(333.89);

O.writeBoolean(false);

O.writeChar('X');

O.close();

o.close();

//read primitive data from file A

FileInputStream i = new FileInputStream("A.txt"); //open file A for read

DataInputStream I = new DataInputStream(i);

System.out.println(I.readInt());

System.out.println(I.readDouble());

System.out.println(I.readBoolean());

System.out.println(I.readChar());

I.close();

i.close();

}

Output:

1999

333.89

false

Character Stream I/O in Java

In a java programming, like a Byte stream Character stream is also used for input-output for 16 bit. But Byte streams are used to perform input and output of 8-bit.

Most common Character streams classes are, FileReader and FileWriter.

FileReader- FileReader uses for reads two bytes at a time.

FileWriter– FileWriter uses for writes two bytes at a time.

Example: Write a program, to copy the content of file A into file B using Byte stream class.

import java.io.*;
public class FileReaderExample {
    public static void main(String arg[]) throws IOException {
        FileReader I = null;
        FileWriter O = null;
        try {
            I = new FileReader("A.txt");
            O = new FileWriter("B.txt");
            int c;
            while ((c = I.read()) != -1) {
                O.write(c);
            }
        } finally {
            if (I != null) {
                I.close();
            }
            if (O != null) {
                O.close();
            }
        }
    }
}

import java.io.*;

public class FileReaderExample {

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

FileReader I = null;

FileWriter O = null;

try {

I = new FileReader("A.txt");

O = new FileWriter("B.txt");

int c;

while ((c = I.read()) != -1) {

O.write(c);

}

} finally {

if (I != null) {

I.close();

}

if (O != null) {

O.close();

}

Note: if there is only file A in which data is written and no file B then, file B will be create automatically.

Suppose we have a File “A”

Hello students I am aditya.

Output: When we run above program one new file create with Name “B” and content of file “A” will be copy into file “B”.

File “B”

Hello students I am aditya.

Byte Streams in Java

In java programming, to perform input and output of 8-bit, Byte stream is used.

Most common byte streams classes are, FileInputStream and FileOutputStream.

FileInputStream : FileInputStream is used for reads one byte at a time .

FileOutputStream : FileOutputStream is used for writes one byte at a time

Writing Bytes

Example: Write a program, to write a bytes to a file using Byte stream class.

import java.io.*;
public class WriteBytes {
    public static void main(String args[]) throws IOException {
        byte b[] = {
            'h',
            'e',
            'l',
            'l',
            'o',
            'a',
            'd',
            'i'
        }; //create a byte array	
        FileOutputStream out = null;
        try {
            out = new FileOutputStream("A.txt"); //open file A for write		
            out.write(b); // write byte data to file output
        } finally {
            out.close();
        }
    }
}

import java.io.*;

public class WriteBytes {

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

byte b[] = {

'h',

'e',

'l',

'o',

'a',

'd',

'i'

}; //create a byte array

FileOutputStream out = null;

try {

out = new FileOutputStream("A.txt"); //open file A for write

out.write(b); // write byte data to file output

} finally {

out.close();

}

Result

checking file A.txt it will show following content.

Note: If there is no file A then, file A will be create automatically

helloadi

helloadi

Reading bytes from a file

Suppose we have a file “A.txt”

Hello Students I am Aditya

Example: Write a program, to read a bytes from file A using Byte stream class and print on output screen.

import java.io.*;
public class ReadBytes {
    public static void main(String args[]) throws IOException {
        FileInputStream in = null;
        try { in = new FileInputStream("A.txt");
            int c;
            while ((c = in .read()) != -1) {
                System.out.print((char) c);
            }
        } finally { in .close();
        }
    }
}

import java.io.*;

public class ReadBytes {

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

FileInputStream in = null;

try { in = new FileInputStream("A.txt");

int c;

while ((c = in .read()) != -1) {

System.out.print((char) c);

}

} finally { in .close();

}

Hello Students I am Aditya

1	Hello Students I am Aditya

Example: Write a program, to copy the content of file A into file B using Byte stream class.

Note: if there is only file A in which data is written and no file B then, file B will be create automatically.

Suppose we have a File “A”

Hello students I am aditya.

Output: When we run above program one new file create with Name “B” and content of file “A” will be copy into file “B”.

File “B”

Hello students I am aditya.

File and Input Output in Java

In Java programming, to perform the input-output in file handling Java has a java.io package which contain contains nearly every class you might ever need.

In file handling streams represent an input source and an output destination.

Stream

In java programming, a sequence of data defined as a “stream”.

Simply there are two type of streams:

InputStream − To read data from a source InputStream is used.
OutputStream- To write a data to a destination OutputStream is used.

Stream Classes

In java, package “java.io” contains a large number of stream classes and these classes can be divided into two groups:

Byte stream
Character stream