DataInputStream

In this chapter you will learn:

How to use DataInputStream
Read with DataInputStream
Use underline BufferedInputStream
DataOutputStream and network stream

Use DataInputStream

DataInputStream enable you to read primitive data from a stream. It implements DataInput interface.

DataInput interface defines methods that convert primitive values from a sequence of bytes.

DataInputStream makes it easy to store binary data, such as integers or floating-point values, in a file. DataInputStream extends FilterInputStream, which extends InputStream, and it implements the DataInput interface.

Here is its only constructor:

DataInputStream(InputStream inputStream)

inputStream specifies the input stream from which data will be read.

DataInputStream reads a sequence of bytes and convert them into values of a primitive type. Here is a sampling of these methods:

double readDouble( ) throws IOException 
boolean readBoolean( ) throws IOException 
int readInt( ) throws IOException

The following code creates a DataInputStream from FileInputStream.

import java.io.DataInputStream;
import java.io.FileInputStream;
/*j ava2  s. c  om*/
public class MainClass {
  public static void main(String args[]) {
    try {
      FileInputStream fis = new FileInputStream("fileName.dat");

      // Create a data input stream
      DataInputStream dis = new DataInputStream(fis);


      // Close file input stream
      fis.close();
    } catch (Exception e) {
      System.out.println("Exception: " + e);
    }
  }
}

Read with DataInputStream

The following program demonstrates the use of DataInputStream:

import java.io.DataInputStream;
import java.io.FileInputStream;
//from   ja v  a2s  .  c o  m
public class MainClass {

  public static void main(String args[]) {
    try {

      FileInputStream fis = new FileInputStream("fileName.dat");

      // Create a data input stream
      DataInputStream dis = new DataInputStream(fis);

      // Read and display data
      System.out.println(dis.readBoolean());
      System.out.println(dis.readByte());
      System.out.println(dis.readChar());
      System.out.println(dis.readDouble());
      System.out.println(dis.readFloat());
      System.out.println(dis.readInt());
      System.out.println(dis.readLong());
      System.out.println(dis.readShort());

      // Close file input stream
      fis.close();
    } catch (Exception e) {
      System.out.println("Exception: " + e);
    }
  }
}

Use underline BufferedInputStream

In order to make the reading from DataInputStream faster. We can wrap stream into BufferedInputStream.

import java.io.BufferedInputStream;
import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.IOException;
//  j  av a 2 s  . c  o  m
public class Main {
  public static void main(String[] args) throws IOException {
    DataInputStream dis = 
      new DataInputStream(
          new BufferedInputStream(
               new FileInputStream("temp.tmp")));
    dis.close();

  }
}

DataOutputStream and network stream

The following code illustrates how to read from a network stream with DataOutputStream. It connects to a server with Socket class and open a stream to read.

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.Socket;
/*from   j  a  va 2s. c  o  m*/
public class MainClass {
  public static void main(String[] args) throws Exception {
    String serverName = args[0];
    int port = Integer.parseInt(args[1]);

    try {
      Socket client = new Socket(serverName, port);

      System.out.println("Just connected to " + client.getRemoteSocketAddress());

      OutputStream outToServer = client.getOutputStream();
      DataOutputStream out = new DataOutputStream(outToServer);
      out.writeUTF("Hello from " + client.getLocalSocketAddress());

      InputStream inFromServer = client.getInputStream();
      DataInputStream in = new DataInputStream(inFromServer);
      System.out.println("Server says " + in.readUTF());

      client.close();
    } catch (IOException e) {
      e.printStackTrace();
    }
  }
}

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What you will learn in the next chapter:

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