ByteArrayInputStream and ByteArrayOutputStream classes and its methods with examples

ByteArrayInputStream class:

• Syntax: 

         java.lang.Object
                 java.io.InputStream
                         java.io.ByteArrayInputStream

• The Byte Array InputStream is composed of three words.
• The Byte means a collection of 8 bits.
• An Array means a collection of the same data type.
• The ByteArray means an array of bytes.
• The InputStream is a class to read from file. 
• So, it can be used to read byte array as an input stream.
• A ByteArrayInputStream contains an internal buffer that contains bytes that may be read from the stream. 
• An internal counter keeps track of the next byte to be supplied by the read method.
• Closing a ByteArrayInputStream has no effect. 
• The methods in this class can be called after the stream has been closed without generating an IOException.
• It has four fields, two constructors, and seven methods.
• Field: 
• 1. buf:
• Syntax:protected byte[] buf
• Use:
• An array of bytes that was provided by the creator of the stream. 
• Elements buf[0] through buf[count-1] are the only bytes that can ever be read from the stream; element buf[pos] is the next byte to be read.
• 2. pos:
• Syntax: protected int pos
• Use: 
• The index of the next character to read from the input stream buffer. 
• This value should always be nonnegative and not larger than the value of count. 
• The next byte to be read from the input stream buffer will be buf[pos].
• 3. mark:
• Syntax: protected int mark
• Use:
• The currently marked position in the stream. 
• ByteArrayInputStream objects are marked at position zero by default when constructed. 
• They may be marked at another position within the buffer by the mark() method. 
• The current buffer position is set to this point by the reset() method.
• 4. count:
• Syntax: protected int count
• Use:
• The index one greater than the last valid character in the input stream buffer.
• This value should always be nonnegative and not larger than the length of buf. 
• It is one greater than the position of the last byte within buf that can ever be read from the input stream buffer.
• Constructor: 
• Syntax:
• public ByteArrayInputStream(byte[] buf)
• public ByteArrayInputStream(byte[] buf, int offset, int length)
• Use:
• Creates a ByteArrayInputStream so that it uses buf as its buffer array. The buffer array is not copied. The initial value of pos is 0 and the initial value of count is the length of buf.
• The initial value of pos is offset and the initial value of count is the minimum of offset+length and buf.length. The buffer array is not copied. The buffer's mark is set to the specified offset.
• Parameters:
• buf - the input buffer.
• offset - the offset in the buffer of the first byte to read.
• length - the maximum number of bytes to read from the buffer.
• Methods:
• 1. available
• It is an overridden method from the InputStream class.
• Note: for more details: See InputStream Class (Methods: 02)
• 2. close
• It is an overridden method from the InputStream class.
• Note: for more details: See InputStream Class (Methods: 03)
• 3. mark
• It is an overridden method from the InputStream class.
• Note: for more details: See InputStream Class (Methods: 04)
• 4. markSupported
• It is an overridden method from the InputStream class.
• Note: for more details: See InputStream Class (Methods: 05)
• 5. read
• It is an overridden method from the InputStream class.
• Note: for more details: See InputStream Class (Methods: 01)
• 6. reset
• It is an overridden method from the InputStream class.
• Note: for more details: See InputStream Class (Methods: 06)
• 7. skip
• It is an overridden method from the InputStream class.
• Note: for more details: See InputStream Class (Methods: 07)

ByteArrayOutputStream class:

• Syntax: 

         java.lang.Object
                 java.io.OutputStream
                         java.io.ByteArrayOutputStream

• The Byte Array OutputStream is composed of three words.
• The Byte means a collection of 8 bits.
• An Array means a collection of the same data type.
• The ByteArray means an array of bytes.
• The OutputStream is a class to write into file. 
• This class implements an output stream in which the data is written into a byte array. 
• The buffer automatically grows as data is written to it. 
• The data can be retrieved using toByteArray() and toString().
• It has two fields, two constructors, and seven methods.
• The four methods derived from the OutputStreamReader class.
• The two methods derived from the Writer class.
• The nine methods derived from the Object class.
• Field: 
• 1. buf: protected byte[] buf
• Use: The buffer where data is stored.
• 2. count: protected int count
• Use: The number of valid bytes in the buffer.
• Constructor: 
• Syntax:
• public ByteArrayOutputStream()
• public ByteArrayOutputStream(int size)
• Use:
• Creates a new byte array output stream. The buffer capacity is initially 32 bytes, though its size increases if necessary.
• Creates a new byte array output stream, with a buffer capacity of the specified size, in bytes.
• Parameters: size - the initial size.
• Throws: IllegalArgumentException - if size is negative.
• Methods:
• 1. close
• It is an overridden method from the OutputStream class.
• Note: for more details: See OutputStream Class (Methods: 01)
• 2. reset
• Syntax: public void reset()
• Use: 
• Resets the count field of this byte array output stream to zero, so that all currently accumulated output in the output stream is discarded. 
• The output stream can be used again, reusing the already allocated buffer space.
• 3. size
• Syntax: public int size()
• Use: Returns the current size of the buffer.
• Returns:
• The value of the count field, which is the number of valid bytes in this output stream.
• 4. toByteArray
• Syntax: public byte[] toByteArray()
• Use: 
• Creates a newly allocated byte array. 
• Its size is the current size of this output stream and the valid contents of the buffer have been copied into it.
• Returns:
• The current contents of this output stream, as a byte array.
• 5. toString
• Syntax: public String toString()
• Use:
• Converts the buffer's contents into a string decoding bytes using the platform's default character set. 
• The length of the new String is a function of the character set, and hence may not be equal to the size of the buffer.
• Returns:
• String decoded from the buffer's contents.
• 6. write
• It is an overridden method from the OutputStream class.
• Note: for more details: See OutputStream Class (Methods: 03)
• 7. writeTo
• Syntax: public void writeTo(OutputStream out) throws IOException
• Use:
• Writes the complete contents of this byte array output stream to the specified output stream argument, as if by calling the output stream's write method using out.write(buf, 0, count).
• Parameters:
• out - the output stream to which to write the data.
• Throws:
• IOException - if an I/O error occurs.

Example (Read Byte Array):

• Step 01: Write a JAVA program.
  
• Step 02: Enjoy the Output.
  

Example (Write Byte Array):

• Step 01: Write a JAVA program.
  
• Step 02: Enjoy the Output.