Java by API/java.io/RandomAccessFile

new RandomAccessFile(String fileName, String mode)

  
/*
 * Output:
 *  
 */
import java.io.RandomAccessFile;
public class MainClass {
  public static void main(String args[]) {
    try {
      RandomAccessFile raf = new RandomAccessFile(args[0], "r");
      long position = raf.length();
      while (position > 0) {
        position -= 1;
        raf.seek(position);
        byte b = raf.readByte();
        System.out.print((char) b);
      }
    } catch (Exception e) {
      e.printStackTrace();
    }
  }
}

RandomAccessFile: close()

  
import java.io.File;
import java.io.FileInputStream;
import java.io.RandomAccessFile;
import java.util.zip.ZipEntry;
import java.util.zip.ZipInputStream;
public class Main {
  public static void main(String[] args) throws Exception{
    ZipInputStream zipinputstream = new ZipInputStream(new FileInputStream("filename"));
    ZipEntry zipentry = zipinputstream.getNextEntry();
    while (zipentry != null) {
      String entryName = zipentry.getName();
      File newFile = new File(entryName);
      String directory = newFile.getParent();
      if (directory == null) {
        if (newFile.isDirectory())
          break;
      }
      RandomAccessFile  rf = new RandomAccessFile(entryName, "r");
      String line;
      if ((line = rf.readLine()) != null) {
        System.out.println(line);
      }
      rf.close();
      zipinputstream.closeEntry();
      zipentry = zipinputstream.getNextEntry();
    }
    zipinputstream.close();
  }
}

RandomAccessFile: getChannel()

  
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
public class MainClass {
  public static void main(String args[]) {
    RandomAccessFile randomAccessFile;
    FileChannel fileChannel;
    ByteBuffer byteBuffer;
    try {
      randomAccessFile = new RandomAccessFile("test.txt", "rw");
      fileChannel = randomAccessFile.getChannel();
      byteBuffer = fileChannel.map(FileChannel.MapMode.READ_WRITE, 0, 26);
      for (int i = 0; i < 10; i++)
        byteBuffer.put((byte) ("A" + i));
      fileChannel.close();
      randomAccessFile.close();
    } catch (IOException exc) {
      System.out.println(exc);
      System.exit(1);
    }
  }
}

RandomAccessFile: getFilePointer()

 
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.channels.FileChannel;
public class Main {
  public static void main(String[] argv) throws IOException {
    RandomAccessFile randomAccessFile = new RandomAccessFile("test.dat", "r");
    randomAccessFile.seek(1000);
    FileChannel fileChannel = randomAccessFile.getChannel();
    // This will print "1000"
    System.out.println("file pos: " + fileChannel.position());
    randomAccessFile.seek(500);
    // This will print "500"
    System.out.println("file pos: " + fileChannel.position());
    fileChannel.position(200);
    // This will print "200"
    System.out.println("file pos: " + randomAccessFile.getFilePointer());
  }
}

RandomAccessFile: length()

  
/*
 * Output:
 *  
 */
import java.io.RandomAccessFile;
public class MainClass {
  public static void main(String args[]) {
    try {
      RandomAccessFile raf = new RandomAccessFile(args[0], "r");
      long position = raf.length();
      while (position > 0) {
        position -= 1;
        raf.seek(position);
        byte b = raf.readByte();
        System.out.print((char) b);
      }
    } catch (Exception e) {
      e.printStackTrace();
    }
  }
}

RandomAccessFile: readBoolean()

 
import java.io.IOException;
import java.io.RandomAccessFile;
public class Main {
  public static void main(String args[]) throws IOException {
    RandomAccessFile file = new RandomAccessFile("test.txt", "rw");
    file.writeBoolean(true);
    file.writeInt(123456);
    file.writeChar("j");
    file.writeDouble(1234.56);
    file.seek(1);
    System.out.println(file.readInt());
    System.out.println(file.readChar());
    System.out.println(file.readDouble());
    file.seek(0);
    System.out.println(file.readBoolean());
    file.close();
  }
}

RandomAccessFile: readByte()

  
/*
 * Output:
 *  
 */
import java.io.RandomAccessFile;
public class MainClass {
  public static void main(String args[]) {
    try {
      RandomAccessFile raf = new RandomAccessFile(args[0], "r");
      long position = raf.length();
      while (position > 0) {
        position -= 1;
        raf.seek(position);
        byte b = raf.readByte();
        System.out.print((char) b);
      }
    } catch (Exception e) {
      e.printStackTrace();
    }
  }
}

RandomAccessFile: read(byte[] b)

 
import java.io.RandomAccessFile;
public class Main {
  public static void main(String[] args) throws Exception {
    RandomAccessFile randomAccessFile = null;
    String line1 = "line\n";
    String line2 = "asdf1234\n";
    // read / write permissions
    randomAccessFile = new RandomAccessFile("yourFile.dat", "rw");
    randomAccessFile.writeBytes(line1);
    randomAccessFile.writeBytes(line2);
    // Place the file pointer at the end of the first line
    randomAccessFile.seek(line1.length());
    byte[] buffer = new byte[line2.length()];
    randomAccessFile.read(buffer);
    System.out.println(new String(buffer));
    randomAccessFile.close();
  }
}

RandomAccessFile: readChar()

 

import java.io.File;
import java.io.RandomAccessFile;
public class Main {
  public static void main(String[] argv) throws Exception {
    File f = new File("filename");
    RandomAccessFile raf = new RandomAccessFile(f, "rw");
    // Read a character
    char ch = raf.readChar();
    // Seek to end of file
    raf.seek(f.length());
    // Append to the end
    raf.writeChars("aString");
    raf.close();
  }
}

RandomAccessFile: readDouble()

 
import java.io.IOException;
import java.io.RandomAccessFile;
public class Main {
  public static void main(String[] args) throws IOException {
    RandomAccessFile rf = new RandomAccessFile("test.dat", "rw");
    for (int i = 0; i < 10; i++)
      rf.writeDouble(i * 1.414);
    rf.close();
    rf = new RandomAccessFile("test.dat", "rw");
    rf.seek(5 * 8);
    rf.writeDouble(47.0001);
    rf.close();
    rf = new RandomAccessFile("test.dat", "r");
    for (int i = 0; i < 10; i++)
      System.out.println("Value " + i + ": " + rf.readDouble());
    rf.close();
  }
}

RandomAccessFile: readInt()

 
import java.io.IOException;
import java.io.RandomAccessFile;
public class Main {
  public static void main(String[] args) {
    try {
      RandomAccessFile raf = new RandomAccessFile("c:\\temp\\RAFsample.txt", "rw");
      raf.writeInt(10);
      raf.writeInt(43);
      raf.writeInt(88);
      raf.writeInt(455);
      raf.seek((3 - 1) * 4);
      raf.writeInt(99);
      raf.seek(0); 
      int i = raf.readInt();
      while (i != -1) {
        System.out.println(i);
        i = raf.readInt();
      }
      raf.close();
    } catch (IOException e) {
    }
  }
}

RandomAccessFile: readLine()

  
import java.io.File;
import java.io.FileInputStream;
import java.io.RandomAccessFile;
import java.util.zip.ZipEntry;
import java.util.zip.ZipInputStream;
public class Main {
  public static void main(String[] args) throws Exception{
    ZipInputStream zipinputstream = new ZipInputStream(new FileInputStream("filename"));
    ZipEntry zipentry = zipinputstream.getNextEntry();
    while (zipentry != null) {
      String entryName = zipentry.getName();
      File newFile = new File(entryName);
      String directory = newFile.getParent();
      if (directory == null) {
        if (newFile.isDirectory())
          break;
      }
      RandomAccessFile  rf = new RandomAccessFile(entryName, "r");
      String line;
      if ((line = rf.readLine()) != null) {
        System.out.println(line);
      }
      rf.close();
      zipinputstream.closeEntry();
      zipentry = zipinputstream.getNextEntry();
    }
    zipinputstream.close();
  }
}

RandomAccessFile: seek(long pos)

  
/*
 * Output:
 *  
 */
import java.io.RandomAccessFile;
public class MainClass {
  public static void main(String args[]) {
    try {
      RandomAccessFile raf = new RandomAccessFile(args[0], "r");
      long position = raf.length();
      while (position > 0) {
        position -= 1;
        raf.seek(position);
        byte b = raf.readByte();
        System.out.print((char) b);
      }
    } catch (Exception e) {
      e.printStackTrace();
    }
  }
}

RandomAccessFile: writeBoolean(boolean v)

 
import java.io.IOException;
import java.io.RandomAccessFile;
public class Main {
  public static void main(String args[]) throws IOException {
    RandomAccessFile file = new RandomAccessFile("test.txt", "rw");
    file.writeBoolean(true);
    file.writeInt(123456);
    file.writeChar("j");
    file.writeDouble(1234.56);
    file.seek(1);
    System.out.println(file.readInt());
    System.out.println(file.readChar());
    System.out.println(file.readDouble());
    file.seek(0);
    System.out.println(file.readBoolean());
    file.close();
  }
}

RandomAccessFile: write(byte[] b)

 
import java.io.RandomAccessFile;
public class Main {
  public static void main(String[] argv) throws Exception {
    RandomAccessFile file = new RandomAccessFile("scores.html", "rw");
    for (int i = 1; i <= 6; i++) {
      System.out.println(file.readLine());
    }
    long current = file.getFilePointer();
    file.seek(current + 6);
    file.write("34".getBytes());
    for (int i = 1; i <= 5; i++) {
      System.out.println(file.readLine());
    }
    current = file.getFilePointer();
    file.seek(current + 6);
    file.write("27".getBytes());
    file.close();
  }
}

RandomAccessFile: writeBytes(String s)

 
import java.io.RandomAccessFile;
public class Main {
  public static void main(String[] args) throws Exception {
    RandomAccessFile randomAccessFile = null;
    String line1 = "line\n";
    String line2 = "asdf1234\n";
    // read / write permissions
    randomAccessFile = new RandomAccessFile("yourFile.dat", "rw");
    randomAccessFile.writeBytes(line1);
    randomAccessFile.writeBytes(line2);
    // Place the file pointer at the end of the first line
    randomAccessFile.seek(line1.length());
    byte[] buffer = new byte[line2.length()];
    randomAccessFile.read(buffer);
    System.out.println(new String(buffer));
    randomAccessFile.close();
  }
}

RandomAccessFile: writeChar(int v)

 
import java.io.IOException;
import java.io.RandomAccessFile;
public class Main {
  public static void main(String args[]) throws IOException {
    RandomAccessFile file = new RandomAccessFile("test.txt", "rw");
    file.writeBoolean(true);
    file.writeInt(123456);
    file.writeChar("j");
    file.writeDouble(1234.56);
    file.seek(1);
    System.out.println(file.readInt());
    System.out.println(file.readChar());
    System.out.println(file.readDouble());
    file.seek(0);
    System.out.println(file.readBoolean());
    file.close();
  }
}

RandomAccessFile: writeChars(String s)

 

import java.io.File;
import java.io.RandomAccessFile;
public class Main {
  public static void main(String[] argv) throws Exception {
    File f = new File("filename");
    RandomAccessFile raf = new RandomAccessFile(f, "rw");
    // Read a character
    char ch = raf.readChar();
    // Seek to end of file
    raf.seek(f.length());
    // Append to the end
    raf.writeChars("aString");
    raf.close();
  }
}

RandomAccessFile: writeDouble(double v)

 
import java.io.IOException;
import java.io.RandomAccessFile;
public class Main {
  public static void main(String args[]) throws IOException {
    RandomAccessFile file = new RandomAccessFile("test.txt", "rw");
    file.writeBoolean(true);
    file.writeInt(123456);
    file.writeChar("j");
    file.writeDouble(1234.56);
    file.seek(1);
    System.out.println(file.readInt());
    System.out.println(file.readChar());
    System.out.println(file.readDouble());
    file.seek(0);
    System.out.println(file.readBoolean());
    file.close();
  }
}

RandomAccessFile: writeInt(int v)

 
import java.io.IOException;
import java.io.RandomAccessFile;
public class Main {
  public static void main(String[] args) {
    try {
      RandomAccessFile raf = new RandomAccessFile("c:\\temp\\RAFsample.txt", "rw");
      raf.writeInt(10);
      raf.writeInt(43);
      raf.writeInt(88);
      raf.writeInt(455);
      raf.seek((3 - 1) * 4);
      raf.writeInt(99);
      raf.seek(0); 
      int i = raf.readInt();
      while (i != -1) {
        System.out.println(i);
        i = raf.readInt();
      }
      raf.close();
    } catch (IOException e) {
    }
  }
}

RandomAccessFile: writeUTF(String str)

 
import java.io.IOException;
import java.io.RandomAccessFile;
public class Main {
  public static void main(String[] args) throws IOException {
    RandomAccessFile raf = new RandomAccessFile("employee.dat", "rw");
    raf.writeUTF("J");
    raf.writeUTF("S");
    raf.writeDouble(4.0);
    raf.seek(0L);
    String fname = raf.readUTF();
    String lname = raf.readUTF();
    double salary = raf.readDouble();
    System.out.println("First name = " + fname);
    System.out.println("Last name = " + lname);
    System.out.println("Salary = " + salary);
    raf.close();
  }
}