import java.nio.*;
import java.io.*;
import java.util.Arrays;

public class ByteBufferReadWriteTest {
  
  /* this method is only for debugging.
   * Comment out code, where method is called.
   */
  public static void print_array(byte[] array) {
    int i=0;
    for(byte b: array) {
      System.out.format("%x", b);
      if(++i % 2 == 0)
        System.out.print(" ");
    }
    System.out.println();
  }
  
  public static void main(String []args ) {
    File file = new File("file.bin");
    write(file);
    read(file);
  }
  
  public static void write(File file) {
    int a = -159954;
    double b = 125.128953;
    char c = 'θ';
    String str = "Πώς είσαι;";
    
    ByteBuffer buffer = ByteBuffer.allocate(512);
    buffer.order(ByteOrder.BIG_ENDIAN);
    buffer.putInt(a);
    buffer.putDouble(b);
    buffer.putChar(c);
    buffer.put(str.getBytes(java.nio.charset.StandardCharsets.UTF_8));
    int buffer_size = buffer.position();
    
    try(FileOutputStream out = new FileOutputStream(file)) {
      byte []array = buffer.array();
      array = Arrays.copyOf(array, buffer_size);
      out.write(array);
      // just for debugging purposes
      //print_array(array);
    }
    catch(IOException ex) {
      System.out.println("Cannot write to file: "+file.getName());  
    }
  }
  
  public static void read(File file) {
    int a;
    double b;
    double c;
    
    byte array[] = new byte[512];
    int read_size;
    try(FileInputStream in = new FileInputStream(file)) {
      read_size = in.read(array);
      array = Arrays.copyOf(array, read_size);
    }
    catch(IOException ex) {
       System.out.println("Cannot read from file: "+file.getName()); 
    }
    // just for debugging purposes
    //print_array(array);
    
    ByteBuffer buffer = ByteBuffer.wrap(array);
    buffer.order(ByteOrder.BIG_ENDIAN);
    System.out.println(buffer.getInt());
    System.out.println(buffer.getDouble());
    System.out.println("'"+buffer.getChar()+"'");
    int str_size = buffer.remaining();
    byte[] bytes = new byte[str_size];
    buffer.get(bytes);
    System.out.println(new String(bytes, java.nio.charset.StandardCharsets.UTF_8));
  }
}