import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

public class FileStreamDemo {

    private final String datei = "zahlen.dat";

    public static void liesDatenAusDatei() {
        DataInputStream dis = null;
        try {
            dis = new DataInputStream(
                    new BufferedInputStream(
                    new FileInputStream(datei)));

            System.out.println(dis.readInt());
            System.out.println(dis.readDouble());

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (dis != null) dis.close();
            } catch (IOException ioe){}
        }
    }

    public static void schreibeDatenInDatei() {
        DataOutputStream dos = null;
        try {
            dos = new DataOutputStream(
                    new BufferedOutputStream(
                    new FileOutputStream(datei)));

            dos.writeInt(-5);
            dos.writeDouble(Math.PI);

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (dos != null) dos.close();
            } catch (IOException ioe){}
        }
    }

    public static void main(String[] args) {
        schreibeDatenInDatei();
        liesDatenAusDatei();
    }
}