Java/File Input Output/DataInputStream

Check the class version

 
import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.IOException;
public class Main {
  public static void main(String[] args) throws IOException {
    DataInputStream in = new DataInputStream(new FileInputStream("Main.class"));
    int start = in.readInt();
    if (start != 0xcafebabe) {
      System.out.println("not valid");
    }
    in.close();
    System.out.println(in.readUnsignedShort()+"/"+in.readUnsignedShort());
    
  }
}

Create DataInputStream from FileInputStream and read different types of data

 
import java.io.DataInputStream;
import java.io.FileInputStream;
class DataInputStreamDemo {
  public static void main(String args[]) throws Exception {
    FileInputStream fis = new FileInputStream(args[0]);
    DataInputStream dis = new DataInputStream(fis);
    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());
    fis.close();
  }
}

DataOutputStream and DataInputStream: read and write by data types

 
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;
public class Main {
  public static void main(String[] atgs) throws Exception {
    DataOutputStream out = new DataOutputStream(new BufferedOutputStream(new FileOutputStream("java.txt")));
    out.writeUTF("");
    out.writeBytes("a");
    out.writeChars("aaa");
    out.close();
    DataInputStream in = new DataInputStream(new BufferedInputStream(new FileInputStream("java.txt")));
    System.out.println(in.readUTF());
    byte[] buf = new byte[1024];
    int len = in.read(buf);
    System.out.println(new String(buf, 0, len));
    in.close();
  }
}

new DataInputStream(new BufferedInputStream(new FileInputStream()))

 

/*
 * Copyright (c) 1995 - 2008 Sun Microsystems, Inc.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   - Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 *   - Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *
 *   - Neither the name of Sun Microsystems nor the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.EOFException;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
public class DataStreams {
  static final String dataFile = "invoicedata";
  static final double[] prices = { 19.99, 9.99, 15.99, 3.99, 4.99 };
  static final int[] units = { 12, 8, 13, 29, 50 };
  static final String[] descs = { "Java T-shirt", "Java Mug",
      "Duke Juggling Dolls", "Java Pin", "Java Key Chain" };
  public static void main(String[] args) throws IOException {
    DataOutputStream out = null;
    try {
      out = new DataOutputStream(new BufferedOutputStream(new FileOutputStream(
          dataFile)));
      for (int i = 0; i < prices.length; i++) {
        out.writeDouble(prices[i]);
        out.writeInt(units[i]);
        out.writeUTF(descs[i]);
      }
    } finally {
      out.close();
    }
    DataInputStream in = null;
    double total = 0.0;
    try {
      in = new DataInputStream(new BufferedInputStream(new FileInputStream(
          dataFile)));
      double price;
      int unit;
      String desc;
      try {
        while (true) {
          price = in.readDouble();
          unit = in.readInt();
          desc = in.readUTF();
          System.out.format("You ordered %d units of %s at $%.2f%n", unit,
              desc, price);
          total += unit * price;
        }
      } catch (EOFException e) {
      }
      System.out.format("For a TOTAL of: $%.2f%n", total);
    } finally {
      in.close();
    }
  }
}

Read boolean from file using DataInputStream

 
import java.io.DataInputStream;
import java.io.FileInputStream;
public class Main {
  public static void main(String[] args) throws Exception {
    FileInputStream fin = new FileInputStream("C:/n.txt");
    DataInputStream din = new DataInputStream(fin);
    boolean b = din.readBoolean();
    System.out.println("boolean : " + b);
    din.close();
  }
}

Read byte array from file using DataInputStream

 

import java.io.DataInputStream;
import java.io.FileInputStream;
public class Main {
  public static void main(String[] args) throws Exception {
    FileInputStream fin = new FileInputStream("C:/Array.txt");
    DataInputStream din = new DataInputStream(fin);
    byte b[] = new byte[10];
    din.read(b);
    din.close();
  }
}

Read byte from file using DataInputStream

 
import java.io.DataInputStream;
import java.io.FileInputStream;
public class Main {
  public static void main(String[] args) throws Exception {
    FileInputStream fin = new FileInputStream("C:/Byte.txt");
    DataInputStream din = new DataInputStream(fin);
    byte b = din.readByte();
    System.out.println("byte : " + b);
    din.close();
  }
}

Read char from file using DataInputStream

 
import java.io.DataInputStream;
import java.io.FileInputStream;
public class Main {
  public static void main(String[] args) throws Exception{
    FileInputStream fin = new FileInputStream("C:/Char.txt");
    DataInputStream din = new DataInputStream(fin);
    char ch = din.readChar();
    System.out.println("Char : " + ch);
    din.close();
  }
}

Read different data types from DataInputStream

 

/*
 * Copyright (c) 1995 - 2008 Sun Microsystems, Inc.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   - Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 *   - Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *
 *   - Neither the name of Sun Microsystems nor the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.EOFException;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
public class DataStreams {
  static final String dataFile = "invoicedata";
  static final double[] prices = { 19.99, 9.99, 15.99, 3.99, 4.99 };
  static final int[] units = { 12, 8, 13, 29, 50 };
  static final String[] descs = { "Java T-shirt", "Java Mug",
      "Duke Juggling Dolls", "Java Pin", "Java Key Chain" };
  public static void main(String[] args) throws IOException {
    DataOutputStream out = null;
    try {
      out = new DataOutputStream(new BufferedOutputStream(new FileOutputStream(
          dataFile)));
      for (int i = 0; i < prices.length; i++) {
        out.writeDouble(prices[i]);
        out.writeInt(units[i]);
        out.writeUTF(descs[i]);
      }
    } finally {
      out.close();
    }
    DataInputStream in = null;
    double total = 0.0;
    try {
      in = new DataInputStream(new BufferedInputStream(new FileInputStream(
          dataFile)));
      double price;
      int unit;
      String desc;
      try {
        while (true) {
          price = in.readDouble();
          unit = in.readInt();
          desc = in.readUTF();
          System.out.format("You ordered %d units of %s at $%.2f%n", unit,
              desc, price);
          total += unit * price;
        }
      } catch (EOFException e) {
      }
      System.out.format("For a TOTAL of: $%.2f%n", total);
    } finally {
      in.close();
    }
  }
}

Read double from file using DataInputStream

 
import java.io.DataInputStream;
import java.io.FileInputStream;
public class Main {
  public static void main(String[] args) throws Exception {
    FileInputStream fin = new FileInputStream("C:/read.txt");
    DataInputStream din = new DataInputStream(fin);
    double d = din.readDouble();
    System.out.println("Double : " + d);
    din.close();
  }
}

Read float from file using DataInputStream

 
import java.io.DataInputStream;
import java.io.FileInputStream;
public class Main {
  public static void main(String[] args) throws Exception {
    FileInputStream fin = new FileInputStream("C:/Float.txt");
    DataInputStream din = new DataInputStream(fin);
    float f = din.readFloat();
    System.out.println("float : " + f);
    din.close();
  }
}

Read int from file using DataInputStream

 
import java.io.DataInputStream;
import java.io.FileInputStream;
public class Main {
  public static void main(String[] args) throws Exception {
    FileInputStream fin = new FileInputStream("C:/Int.txt");
    DataInputStream din = new DataInputStream(fin);
    int i = din.readInt();
    System.out.println("int : " + i);
    din.close();
  }
}

Read long from file using DataInputStream

 
import java.io.DataInputStream;
import java.io.FileInputStream;
public class Main {
  public static void main(String[] args) throws Exception {
    FileInputStream fin = new FileInputStream("C:/Long.txt");
    DataInputStream din = new DataInputStream(fin);
    long l = din.readLong();
    System.out.println("long : " + l);
    din.close();
  }
}

Read short from file using DataInputStream

 
import java.io.DataInputStream;
import java.io.FileInputStream;
public class Main {
  public static void main(String[] args) throws Exception {
    FileInputStream fin = new FileInputStream("C:/Short.txt");
    DataInputStream din = new DataInputStream(fin);
    short s = din.readShort();
    System.out.println("short : " + s);
    din.close();
  }
}

Read short type of data with DataInputStream

 

import java.io.DataInputStream;
import java.io.FileInputStream;
class Main {
  public static void main(String args[]) throws Exception {
    FileInputStream fis = new FileInputStream(args[0]);
    DataInputStream dis = new DataInputStream(fis);
    // Read and display data
    System.out.print(dis.readShort() + " ");
    fis.close();
  }
}

Read unsigned byte from file using DataInputStream

 
import java.io.DataInputStream;
import java.io.FileInputStream;
public class Main {
  public static void main(String[] args) throws Exception {
    FileInputStream fin = new FileInputStream("C:/UnsignedByte.txt");
    DataInputStream din = new DataInputStream(fin);
    int i = din.readUnsignedByte();
    System.out.println("Unsinged byte value : " + i);
    din.close();
  }
}

Use DataInputStream to create double

 
import java.io.DataInputStream;
import java.io.FileInputStream;
public class Main {
  public static void main(String[] argv) throws Exception {
    FileInputStream fileIn = new FileInputStream("data.txt");
    DataInputStream dataIn = new DataInputStream(fileIn);
    System.out.println(dataIn.readUTF());
    int counter = dataIn.readInt();
    double sum = 0.0;
    for (int i = 0; i < counter; i++) {
      double current = dataIn.readDouble();
      System.out.println("Just read " + current);
      sum += current;
    }
    System.out.println("\nAverage = " + sum / counter);
    dataIn.close();
    fileIn.close();
  }
}