Java Tutorial/File/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 a compressed data file by using a DeflaterOutputStream and then read that data through an InflaterInputStream.

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.util.zip.DeflaterOutputStream;
import java.util.zip.InflaterInputStream;
public class Main {
  public static void main(String[] argv) throws Exception {
    double data[] = { 1.1, 2.2, 3.3, 4.4, 5.5, 6.6 };
    DataOutputStream fout = new DataOutputStream(new DeflaterOutputStream(new FileOutputStream(
        "data.dat")));
    fout.writeInt(data.length);
    for (double d : data)
      fout.writeDouble(d);
    DataInputStream  fin = new DataInputStream(new InflaterInputStream(new FileInputStream(
        "data.dat")));
    int num = fin.readInt();
    double avg = 0.0;
    double d;
    for (int i = 0; i < num; i++) {
      d = fin.readDouble();
      avg += d;
      System.out.print(d + " ");
    }
    fin.close();
    fout.close();
  }
}

Create DataInputStream from BufferedInputStream and FileInputStream

import java.io.BufferedInputStream;
import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.IOException;
public class MainClass {
  public static void main(String[] args) throws IOException {
    DataInputStream dis = new DataInputStream(new BufferedInputStream(new FileInputStream(
        "temp.tmp")));
    for (int i = 0; i < 10; i++)
      dis.readInt();
    dis.close();
  }
}

Create DataInputStream from ByteArrayInputStream

import java.io.ByteArrayInputStream;
import java.io.DataInputStream;
import java.io.EOFException;
import java.io.IOException;
public class MainClass {
  public static void main(String[] args) throws IOException {
    try {
      DataInputStream in3 = new DataInputStream(
        new ByteArrayInputStream("a dbcde".getBytes()));
      while(true)
        System.out.print((char)in3.readByte());
    } catch(EOFException e) {
      System.err.println("End of stream");
    }

  }
}//

a dbcdeEnd of stream

Create DataInputStream from FileInputStream

import java.io.DataInputStream;
import java.io.EOFException;
import java.io.FileInputStream;
import java.io.IOException;
public class MainClass {
  public static void main(String[] args) throws Exception {
    DataInputStream din = null;
    try {
      FileInputStream fin = new FileInputStream("myfile.dat");
      din = new DataInputStream(fin);
      while (true) {
        int theNumber = din.readInt();
        System.out.println(theNumber);
      }
    } catch (EOFException ex) {
      din.close();
    } catch (IOException ex) {
      System.err.println(ex);
    }
  }
}

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 double and UTF from DataInputStream with BufferedInputStream backended

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
public class MainClass {
  public static void main(String[] args) throws IOException {
    DataOutputStream out2 = new DataOutputStream(new BufferedOutputStream(new FileOutputStream(
        "Data.txt")));
    out2.writeDouble(3.14159);
    out2.writeUTF("Square root of 2");
    out2.close();
    DataInputStream in5 = new DataInputStream(new BufferedInputStream(new FileInputStream(
        "Data.txt")));
    System.out.println(in5.readDouble());
    System.out.println(in5.readUTF());
  }
}

Read double from DataInputStream

import java.io.DataInputStream;
import java.io.EOFException;
import java.io.FileInputStream;
import java.io.IOException;
public class MainClass {
  public static void main(String[] args) {
    try {
      FileInputStream fin = new FileInputStream("myFile.dat");
      DataInputStream din = new DataInputStream(fin);
      while (true) {
        double theNumber = din.readDouble();
        System.out.println(theNumber);
      }
    } catch (EOFException e) {
    } catch (IOException e) {
      // abnormal termination
      System.err.println(e);
    }
  }
}

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 DataInputStream

import java.io.DataInputStream;
import java.io.EOFException;
import java.io.FileInputStream;
import java.io.IOException;
public class MainClass {
  public static void main(String[] args) throws Exception {
    DataInputStream din = null;
    try {
      FileInputStream fin = new FileInputStream("myfile.dat");
      din = new DataInputStream(fin);
      while (true) {
        int theNumber = din.readInt();
        System.out.println(theNumber);
      }
    } catch (EOFException ex) {
      din.close();
    } catch (IOException ex) {
      System.err.println(ex);
    }
  }
}

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 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();
  }
}

Testing for end of file while reading a byte at a time.

import java.io.BufferedInputStream;
import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.IOException;
public class MainClass {
  public static void main(String[] args) throws IOException {
    DataInputStream in = new DataInputStream(new BufferedInputStream(new FileInputStream(
        "test.java")));
    while (in.available() != 0)
      System.out.print((char) in.readByte());
  }
}

This class is an part implementation of DataInput. It wraps a Reader object.

/* Copyright (c) 2001-2009, The HSQL Development Group
 * 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
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 *
 * Neither the name of the HSQL Development Group 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 HSQL DEVELOPMENT GROUP, HSQLDB.ORG,
 * 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;
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 * 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.DataInput;
import java.io.EOFException;
import java.io.IOException;
import java.io.Reader;
/**
 * This class is an part implementation of DataInput. It wraps a Reader object.
 *
 * @author Fred Toussi (fredt@users dot sourceforge.net)
 * @version 1.9.0
 * @since 1.9.0
 */
public class ReaderDataInput implements DataInput {
    protected Reader reader;
    protected int    pos;
    int              lastChar = -1;
    public ReaderDataInput(Reader reader) {
        this.reader = reader;
        this.pos    = 0;
    }
    // methods that implement java.io.DataInput
    public final void readFully(byte[] b) throws IOException {
        readFully(b, 0, b.length);
    }
    public final void readFully(byte[] bytes, int off,
                                int len) throws IOException {
        if (len < 0) {
            throw new IndexOutOfBoundsException();
        }
        int n = 0;
        while (n < len) {
            int b = read();
            if (b < 0) {
                throw new EOFException();
            }
            bytes[off + n++] = (byte) b;
        }
    }
    public final boolean readBoolean() throws IOException {
        int b = read();
        if (b < 0) {
            throw new EOFException();
        }
        return (b != 0);
    }
    public final byte readByte() throws IOException {
        int b = read();
        if (b < 0) {
            throw new EOFException();
        }
        return (byte) b;
    }
    public final int readUnsignedByte() throws IOException {
        int b = read();
        if (b < 0) {
            throw new EOFException();
        }
        return b;
    }
    public short readShort() throws IOException {
        int b1 = read();
        if (b1 < 0) {
            throw new EOFException();
        }
        int b2 = read();
        if (b2 < 0) {
            throw new EOFException();
        }
        return (short) ((b1 << 8) | b2);
    }
    public final int readUnsignedShort() throws IOException {
        int b1 = read();
        int b2 = read();
        if ((b1 | b2) < 0) {
            throw new EOFException();
        }
        return ((b1 << 8) + (b2));
    }
    public final char readChar() throws IOException {
        int b1 = read();
        int b2 = read();
        if ((b1 | b2) < 0) {
            throw new EOFException();
        }
        return (char) ((b1 << 8) + (b2));
    }
    public int readInt() throws IOException {
        throw new java.lang.RuntimeException("not implemented.");
    }
    public long readLong() throws IOException {
        throw new java.lang.RuntimeException("not implemented.");
    }
    public final float readFloat() throws IOException {
        throw new java.lang.RuntimeException("not implemented.");
    }
    public final double readDouble() throws IOException {
        throw new java.lang.RuntimeException("not implemented.");
    }
    public int skipBytes(int n) throws IOException {
        throw new java.lang.RuntimeException("not implemented.");
    }
    public String readLine() throws IOException {
        throw new java.lang.RuntimeException("not implemented.");
    }
    public String readUTF() throws IOException {
        throw new java.lang.RuntimeException("not implemented.");
    }
    public int read() throws IOException {
        if (lastChar >= 0) {
            int val = lastChar & 0xff;
            lastChar = -1;
            pos++;
            return val;
        }
        lastChar = reader.read();
        if (lastChar < 0) {
            return lastChar;
        }
        pos++;
        return lastChar >> 8;
    }
}

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();
  }
}