What is InputStream Output Stream Why and when do we use them

Question

Someone explain to me what InputStream and OutputStream are   I am confused about the use cases for both InputStream and OutputStream   If you could also include a snippet of code to go along with your explanation  that would be great  Thanks

User · Answer

OutputStream is an abstract class that represents writing output. There are many different OutputStream classes, and they write out to certain things (like the screen, or Files, or byte arrays, or network connections, or etc). InputStream classes access the same things, but they read data in from them.

Here is a good basic example of using FileOutputStream and FileInputStream to write data to a file, then read it back in.

User · Answer

you read from an InputStream and write to an OutputStream   for example  say you want to copy a file  You would create a FileInputStream to read from the source file and a FileOutputStream to write to the new file   If your data is a character stream  you could use a FileReader instead of an InputStream and a FileWriter instead of an OutputStream if you prefer   InputStream input          many different types OutputStream output          many different types  byte   buffer   new byte 1024   int n   0  while   n   input read buffer      -1      output write buffer  0  n    input close    output close

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An output stream is generally related to some data destination like a file or a network etc In java output stream is a destination where data is eventually written and it ends  import java io printstream   class PPrint       static PPrintStream oout   new PPrintStream       class PPrintStream       void print String str             System out println str           class outputstreamDemo       public static void main String args              System out println  hello world            System out prinln  this is output stream demo

User · Answer

Stream  In laymen terms stream is data   most generic stream is binary representation of data    Input Stream   If you are reading data from a file or any other source   stream used is input stream  In a simpler terms input stream acts as a channel to read data     Output Stream   If you want to read and process data from a source  file etc  you first need to save the data   the mean to store data is output stream

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The goal of InputStream and OutputStream is to abstract different ways to input and output  whether the stream is a file  a web page  or the screen shouldn t matter   All that matters is that you receive information from the stream  or send information into that stream    InputStream is used for many things that you read from   OutputStream is used for many things that you write to   Here s some sample code  It assumes the InputStream instr and OutputStream osstr have already been created   int i   while   i   instr read       -1        osstr write i      instr close    osstr close

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A stream is a continuous flow of liquid  air  or gas    Java stream is a flow of data from a source into a destination  The source or destination can be a disk  memory  socket  or other programs  The data can be bytes  characters  or objects  The same applies for C  or C   streams  A good metaphor for Java streams is water flowing from a tap into a bathtub and later into a drainage   The data represents the static part of the stream  the read and write methods the dynamic part of the stream    InputStream represents a flow of data from the source  the OutputStream represents a flow of data into the destination  Finally  InputStream and OutputStream are abstractions over low-level access to data  such as C file pointers

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InputStream is used for reading  OutputStream for writing  They are connected as decorators to one another such that you can read write all different types of data from all different types of sources   For example  you can write primitive data to a file   File file   new File  C  text bin    file createNewFile    DataOutputStream stream   new DataOutputStream new FileOutputStream file    stream writeBoolean true   stream writeInt 1234   stream close      To read the written contents   File file   new File  C  text bin    DataInputStream stream   new DataInputStream new FileInputStream file    boolean isTrue   stream readBoolean    int value   stream readInt    stream close    System out printlin isTrue         value     You can use other types of streams to enhance the reading writing  For example  you can introduce a buffer for efficiency   DataInputStream stream   new DataInputStream      new BufferedInputStream new FileInputStream file       You can write other data such as objects   MyClass myObject   new MyClass       MyClass have to implement Serializable ObjectOutputStream stream   new ObjectOutputStream      new FileOutputStream  C  text obj     stream writeObject myObject   stream close      You can read from other different input sources   byte   test   new byte    0  0  1  0  0  0  1  1  8  9   DataInputStream stream   new DataInputStream new ByteArrayInputStream test    int value0   stream readInt    int value1   stream readInt    byte value2   stream readByte    byte value3   stream readByte    stream close    System out println value0         value1         value2         value3     For most input streams there is an output stream  also  You can define your own streams to reading writing special things and there are complex streams for reading complex things  for example there are Streams for reading writing ZIP format

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From the Java Tutorial   A stream is a sequence of data    A program uses an input stream to read data from a source  one item at a time     A program uses an output stream to write data to a destination  one item at time        The data source and data destination pictured above can be anything that holds  generates  or consumes data  Obviously this includes disk files  but a source or destination can also be another program  a peripheral device  a network socket  or an array    Sample code from oracle tutorial   import java io FileInputStream  import java io FileOutputStream  import java io IOException   public class CopyBytes       public static void main String   args  throws IOException            FileInputStream in   null          FileOutputStream out   null           try               in   new FileInputStream  xanadu txt                out   new FileOutputStream  outagain txt                int c               while   c   in read       -1                    out write c                           finally               if  in    null                    in close                              if  out    null                    out close                                      This program uses byte streams to copy xanadu txt file to outagain txt   by writing one byte at a time  Have a look at this SE question to know more details about advanced Character streams  which are wrappers on top of Byte Streams    byte stream and character stream

[java] What is InputStream & Output Stream? Why and when do we use them?

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