File IO Stream

File IO Stream

File IO Streams provide READ/WRITE access to Files. There two BYTE File IO Streams (FileInputStream and FileOutputStream) and there are two CHARACTER File IO Streams (FileReader and FileWriter).

FileInputStream
FileInputStream takes a File or File name as a Constructor parameter and provides three distinct READ api's to access the file contents.

1. read() :-

• Reads a single byte at a time.
• Blocks if no input is available.
• Returns -1 if EOF is encountered.

  int eachByte;
  FileInputStream fileInputStream = new FileInputStream("fileinputstream.txt");
  
  // Data Structure to contain the Bytes from the File
  byte[] byteContainer = new byte[fileInputStream.available()];
  
  // Reads a single byte at a time.
  // Blocks if no input is available.
  // Returns -1 if EOF is encountered.
  while((eachByte = fileInputStream.read()) != -1)
  {
   System.out.println("An estimate of the remaining bytes --> "+fileInputStream.available());
   byteContainer[(byteContainer.length - 1) - fileInputStream.available()] = (byte)eachByte;;
  }
  
  String fileContent = new String( byteContainer );
  
  System.out.println("fileContent --> \n"+fileContent);
  
  fileInputStream.close();
 

2. read(byte[] b) :-

• Reads number of byte equal to the size of the array or size of the data, which ever is small.
• Blocks if no input is available.
• Returns -1 if EOF is encountered or the number of bytes read.

  FileInputStream fileInputStream = new FileInputStream("fileinputstream.txt");
  
  // Data Structure to contain the Bytes from the File
  byte[] byteContainer = new byte[fileInputStream.available()];
  
  // Reads number of byte equal to the size of the array.
  // Blocks if no input is available.
  // Returns -1 if EOF is encountered or the number of bytes read.
  System.out.println("Number of bytes read --> "+fileInputStream.read(byteContainer));
  
  
  String fileContent = new String( byteContainer );
  
  System.out.println("fileContent --> \n"+fileContent);
  
  fileInputStream.close();
 

3. read(byte[] b, int offset, int length) :-

• Reads starting from the 'offset' number of bytes equal to the 'length' or size of the data, which ever is small.
• Blocks if no input is available.
• Returns -1 if EOF is encountered or the number of bytes read.

  FileInputStream fileInputStream = new FileInputStream("fileinputstream.txt");
  
  // Data Structure to contain the Bytes from the File
  byte[] byteContainer = new byte[fileInputStream.available()];
  
  // Reads number of byte equal to the size of the array.
  // Blocks if no input is available.
  // Returns -1 if EOF is encountered or the number of bytes read.
  System.out.println("Number of bytes read --> "+fileInputStream.read(byteContainer, 5, fileInputStream.available()-5));
   
  String fileContent = new String( byteContainer );
  
  System.out.println("fileContent --> \n"+fileContent);
  
  fileInputStream.close();
  

FileOutputStream
FileOutputStream takes a File or File name as a Constructor parameter and provides three distinct WRITE api's.

1. write() :-

• Writes a single byte at a time.

  //Bytes to be written into the file.
  byte inputByte[] = "1::Hi There !!!\nHow is life".getBytes();
  
  FileOutputStream fileOutputStream = new FileOutputStream("fileoutputstream.txt");
  for(int byteCount = 0; byteCount < inputByte.length; byteCount++)
  {
   // Writes one byte at a time.
   fileOutputStream.write(inputByte[byteCount]);
  }
  
  fileOutputStream.close();
  

2. write(byte[] b) :-

• Writes a complete byte Array at a time.

  //Bytes to be written into the file.
  byte inputByte[] = "2::Hi There !!!\nHow is life".getBytes();
  
  FileOutputStream fileOutputStream = new FileOutputStream("fileoutputstream.txt");
  
  // Writes the whole byte array at once.
  fileOutputStream.write(inputByte);
  
  fileOutputStream.close();
  

3. write(byte[] b, int offset, int length) :-

• Writes a byte Array starting from the 'offset' till the 'length' at a time.

  //Bytes to be written into the file.
  byte inputByte[] = "3::Hi There !!!\nHow is life".getBytes();
  
  FileOutputStream fileOutputStream = new FileOutputStream("fileoutputstream.txt");
  
  // Writes partial byte array at once.
  fileOutputStream.write(inputByte, 5, inputByte.length-5);
  
  fileOutputStream.close();
 
  

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