DAY 8

DAY 8
JAVA IO
Java I/O (Input and Output) is used to process the input and produce the output.
Java uses the concept of stream to make I/O operation fast. The java.io package contains all the classes required for input and output operations.
We can perform file handling in java by Java I/O API.

Stream

A stream is a sequence of data.In Java a stream is composed of bytes. It's called a stream because it is like a stream of water that continues to flow.
In java, 3 streams are created for us automatically. All these streams are attached with console.
1) System.out: standard output stream
2) System.in: standard input stream
3) System.err: standard error stream

OutputStream vs InputStream

The explanation of OutputStream and InputStream classes are given below:

OutputStream

Java application uses an output stream to write data to a destination, it may be a file, an array, peripheral device or socket.

InputStream

Java application uses an input stream to read data from a source, it may be a file, an array, peripheral device or socket.

OutputStream class

OutputStream class is an abstract class. It is the super class of all classes representing an output stream of bytes. An output stream accepts output bytes and sends them to some sink.

Useful methods of OutputStream

MethodDescription
1) public void write(int)throws IOExceptionis used to write a byte to the current output stream.
2) public void write(byte[])throws IOExceptionis used to write an array of byte to the current output stream.
3) public void flush()throws IOExceptionflushes the current output stream.
4) public void close()throws IOExceptionis used to close the current output stream.

OutputStream Hierarchy

Java output stream hierarchy

InputStream class

InputStream class is an abstract class. It is the super class of all classes representing an input stream of bytes.

Useful methods of InputStream

MethodDescription
1) public abstract int read()throws IOExceptionreads the next byte of data from the input stream. It returns -1 at the end of file.
2) public int available()throws IOExceptionreturns an estimate of the number of bytes that can be read from the current input stream.
3) public void close()throws IOExceptionis used to close the current input stream.

InputStream Hierarchy

Java input stream hierarchy

Java FileOutputStream Class

Java FileOutputStream is an output stream used for writing data to a file.
If you have to write primitive values into a file, use FileOutputStream class. You can write byte-oriented as well as character-oriented data through FileOutputStream class. But, for character-oriented data, it is preferred to use FileWriter than FileOutputStream.
Declaration:
public class FileOutputStream extends OutputStream 

for example:
import java.io.FileOutputStream;  
public class FileOutputStreamExample {  
    public static void main(String args[]){    
           try{    
             FileOutputStream fout=new FileOutputStream("D:\\testout.txt");    
             fout.write(65);    
             fout.close();    
             System.out.println("success...");    
            }catch(Exception e){System.out.println(e);}    
      }   
}

Java FileInputStream Class

Java FileInputStream class obtains input bytes from a file. It is used for reading byte-oriented data (streams of raw bytes) such as image data, audio, video etc. You can also read character-stream data. But, for reading streams of characters, it is recommended to use FileReader class.  
Declaration:
public class FileInputStream extends InputStream

for example:
import java.io.FileInputStream;  
public class DataStreamExample {  
     public static void main(String args[]){    
          try{    
            FileInputStream fin=new FileInputStream("D:\\testout.txt");    
            int i=fin.read();  
            System.out.print((char)i);    
  
            fin.close();    
          }catch(Exception e){System.out.println(e);}    
         }    
        }  


Java BufferedOutputStream Class

Java BufferedOutputStream class is used for buffering an output stream. It internally uses buffer to store data. It adds more efficiency than to write data directly into a stream. So, it makes the performance fast.
For adding the buffer in an OutputStream, use the BufferedOutputStream class. Let's see the syntax for adding the buffer in an OutputStream:
OutputStream os= new BufferedOutputStream(new FileOutputStream("D:\\IO Package\\testout.txt")); 

package com.javatpoint;  
import java.io.*;  
public class BufferedOutputStreamExample{    
public static void main(String args[])throws Exception{    
     FileOutputStream fout=new FileOutputStream("D:\\testout.txt");    
     BufferedOutputStream bout=new BufferedOutputStream(fout);    
     String s="Welcome to javaTpoint.";    
     byte b[]=s.getBytes();    
     bout.write(b);    
     bout.flush();    
     bout.close();    
     fout.close();    
     System.out.println("success");    
}    
}  


Java BufferedInputStream Class

Java BufferedInputStream class is used to read information from stream. It internally uses buffer mechanism to make the performance fast.
The important points about BufferedInputStream are:
  • When the bytes from the stream are skipped or read, the internal buffer automatically refilled from the contained input stream, many bytes at a time.
  • When a BufferedInputStream is created, an internal buffer array is created.

Java BufferedInputStream Class

Java BufferedInputStream class is used to read information from stream. It internally uses buffer mechanism to make the performance fast.
The important points about BufferedInputStream are:
  • When the bytes from the stream are skipped or read, the internal buffer automatically refilled from the contained input stream, many bytes at a time.
  • When a BufferedInputStream is created, an internal buffer array is created.

Java BufferedInputStream Class

Java BufferedInputStream class is used to read information from stream. It internally uses buffer mechanism to make the performance fast.
The important points about BufferedInputStream are:
  • When the bytes from the stream are skipped or read, the internal buffer automatically refilled from the contained input stream, many bytes at a time.
  • When a BufferedInputStream is created, an internal buffer array is created.
for example:
package com.javatpoint;  
   
import java.io.*;  
public class BufferedInputStreamExample{    
 public static void main(String args[]){    
  try{    
    FileInputStream fin=new FileInputStream("D:\\testout.txt");    
    BufferedInputStream bin=new BufferedInputStream(fin);    
    int i;    
    while((i=bin.read())!=-1){    
     System.out.print((char)i);    
    }    
    bin.close();    
    fin.close();    
  }catch(Exception e){System.out.println(e);}    
 }    
}  


Java ByteArrayOutputStream Class

Java ByteArrayOutputStream class is used to write common data into multiple files. In this stream, the data is written into a byte array which can be written to multiple streams later.
The ByteArrayOutputStream holds a copy of data and forwards it to multiple streams.
The buffer of ByteArrayOutputStream automatically grows according to data.
for example:

package com.javatpoint;  
import java.io.*;  
public class DataStreamExample {  
public static void main(String args[])throws Exception{    
      FileOutputStream fout1=new FileOutputStream("D:\\f1.txt");    
      FileOutputStream fout2=new FileOutputStream("D:\\f2.txt");    
        
      ByteArrayOutputStream bout=new ByteArrayOutputStream();    
      bout.write(65);    
      bout.writeTo(fout1);    
      bout.writeTo(fout2);    
        
      bout.flush();    
      bout.close();//has no effect    
      System.out.println("Success...");    
     }    
    }   


Java ByteArrayInputStream Class

The ByteArrayInputStream is composed of two words: ByteArray and InputStream. As the name suggests, it can be used to read byte array as input stream.
Java ByteArrayInputStream class contains an internal buffer which is used to read byte array as stream. In this stream, the data is read from a byte array.
The buffer of ByteArrayInputStream automatically grows according to data.
for example:

package com.javatpoint;  
import java.io.*;  
public class ReadExample {  
  public static void main(String[] args) throws IOException {  
    byte[] buf = { 35, 36, 37, 38 };  
    // Create the new byte array input stream  
    ByteArrayInputStream byt = new ByteArrayInputStream(buf);  
    int k = 0;  
    while ((k = byt.read()) != -1) {  
      //Conversion of a byte into character  
      char ch = (char) k;  
      System.out.println("ASCII value of Character is:" + k + "; Special character is: " + ch);  
    }  
  }  
}  



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