Java.io.ByteArrayInputStream class in Java - GeeksforGeeks

12 Oct, 2021
java.io.ByteArrayInputStream class contains all the buffers, containing bytes to be read from the Input Stream. There is no IO exception in case of ByteArrayInputStream class methods. Methods of this class can be called even after closing the Stream, there is no effect of it on the class methods.
Declaration : 
public class ByteArrayInputStream
   extends InputStream
Fields  
protected byte[] buf: An array of bytes that was provided by the creator of the stream.
protected int count: The index one greater than the last valid character in the input stream buffer.
protected int mark: The currently marked position in the stream.
protected int pos: This is the index of the next character to read from the input stream buffer.
Constructors :  
ByteArrayInputStream(byte[] buffer) :creates ByteArrayInputStream to use buffer array – “buffer”.
ByteArrayInputStream(byte[] buf, int offset, int length) :creates ByteArrayInputStream that uses some part of “buffer” i.e. buffer array
Methods:  
mark(int arg) : Java.io.ByteArrayInputStream.mark(int arg) marks the current position of the input stream. It sets readlimit i.e. maximum number of bytes that can be read before mark position becomes invalid. Syntax :
public void mark(int arg)
Parameters :
arg : integer specifying the read limit of the input Stream
Return : 
void
read() : java.io.ByteArrayInputStream.read() reads next byte of data from the Input Stream. The value byte is returned in the range 0 to 255. If no byte is available because the end of the stream has been reached, the value -1 is returned. Method doesn’t block Syntax :
public int read()
Parameters :
------
Return : 
Reads next data else, -1 i.e. when end of file is reached.
Exception :
->  IOException : If I/O error occurs.
close() : java.io.ByteArrayInputStream.close() closes the input stream and releases system resources associated with this stream to Garbage Collector. Syntax :
public void close()
Parameters :
------
Return : 
void
Exception :
->  IOException : If I/O error occurs.
read(byte[] buffer, int offset, int maxlen) : Java.io.ByteArrayInputStream.read(byte[] buffer, int offset, int maxlen) reads “buffer” byte array of Input Stream starting from position “offset” to maxlen. Syntax :
public int read(byte[] buffer, int offset, int maxlen)
Parameters :
arg : array whose number of bytes to be read
offset : starting position in buffer from where to read
maxlen : maximum  no. of bytes to be read
Return : 
 reads number of bytes and return to the buffer else, -1 i.e. when end of file is reached.
Exception :
->  IOException : If I/O error occurs.
->  NullPointerException : if arg is null.
reset() : Java.io.ByteArrayInputStream.reset() is invoked by mark() method. It repositions the input stream to the marked position. Syntax :
public void reset()
Parameters :
----
Return : 
void
Exception :
->  IOException : If I/O error occurs.
markSupported() : Java.io.ByteArrayInputStream.markSupported() method tests if this input stream supports the mark and reset methods. The markSupported method of ByteArrayInputStreamInputStream returns true always Syntax :
public boolean markSupported()
Parameters :
-------
Return : 
true if input stream supports the mark() and reset() method  else,false
skip(long arg) : Java.io.ByteArrayInputStream.skip(long arg) skips arg bytes in the input stream. Syntax :
public long skip(long arg)
Parameters :
arg : no. of bytes to be skipped
Return : 
skip bytes.
Exception :
->  IOException : If I/O error occurs.
available() : Java.io.ByteArrayInputStream.available() tells total no. of bytes from the Input Stream to be read Syntax :
public int available()
Parameters :
-----------
Return : 
total no. of bytes to be read
Exception :
-----------
Java Program explaining ByteArrayInputStream Class methods : 
Java
// Java program illustrating the working of ByteArrayInputStream method// mark(), read(), skip(), available()// markSupported(), close(), reset() import java.io.*; public class NewClass{    public static void main(String[] args) throws Exception    {        byte[] buffer = {71, 69, 69, 75, 83};               ByteArrayInputStream geek = null;        try        {            geek = new ByteArrayInputStream(buffer);                         // Use of available() method : telling the no. of bytes to be read            int number = geek.available();            System.out.println("Use of available() method : " + number);                                            // Use of read() method : reading and printing Characters one by one            System.out.println("\nChar : "+(char)geek.read());            System.out.println("Char : "+(char)geek.read());            System.out.println("Char : "+(char)geek.read());             // Use of mark() :            geek.mark(0);             // Use of skip() : it results in skipping 'k' from "GEEKS"            geek.skip(1);            System.out.println("skip() method comes to play");            System.out.println("mark() method comes to play");            System.out.println("Char : "+(char)geek.read());             // Use of markSupported            boolean check = geek.markSupported();            System.out.println("\nmarkSupported() : " + check);            if(geek.markSupported())            {                // Use of reset() method : repositioning the stream to marked positions.                geek.reset();                System.out.println("\nreset() invoked");                System.out.println("Char : "+(char)geek.read());                System.out.println("Char : "+(char)geek.read());            }            else            {                System.out.println("reset() method not supported.");            }             System.out.println("geek.markSupported() supported reset() : "+check);         }        catch(Exception except)        {            // in case of I/O error            except.printStackTrace();        }        finally        {            // releasing the resources back to the GarbageCollector when closes            if(geek!=null)            {                // Use of close() : closing the file and releasing resources                geek.close();            }        }    }}
Output : 
Use of available() method : 5

Char : G
Char : E
Char : E
skip() method comes to play
mark() method comes to play
Char : S

markSupported() : true

reset() invoked
Char : K
Char : S
geek.markSupported() supported reset() : true
Next Article: io.ByteArrayOutputStream() Class in Java
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