My .dat file can't display double number

Question

I created my sales.dat with these code:

public static void main(String[] args) throws IOException {

    DataOutputStream output = new DataOutputStream
            (new FileOutputStream("E:/HOMEWORK/OOP/OOP-java/src/week2/sales.dat"));

    output.writeChars("San Francisco: ");
    output.writeDouble(1123.456);


}

And when I opened sales.dat, here it is:

I wrote another class to read .dat file:

public static void main(String[] args) throws IOException {

    File file = new File("E:/HOMEWORK/OOP/OOP-java/src/week2/sales.dat");
    FileReader reader = new FileReader(file);

    char[] buffer = new char[4*1024];
    int read = -1;

    StringBuilder builder = new StringBuilder();
    while( (read = reader.read(buffer)) !=-1){
        builder.append(buffer,0,read);
    }
    System.out.println(builder);


//              

}

And the result is :

So plz help me, the output must be :" San Francisco: 1123.456 "

Answer 1

You should use DataInputStream to read.

public static void main(String[] args) throws IOException {
        String name = "...";
        DataOutputStream output = new DataOutputStream
                (new FileOutputStream(name));
        output.writeUTF("San Francisco: ");
        output.writeDouble(1123.456);
        output.close();
}

public static void main(String[] args) throws IOException {
    String name = "C:/Users/hsivakumar/Downloads/sales.dat";

    DataInputStream reader = new DataInputStream(new FileInputStream(name));

    StringBuilder builder = new StringBuilder();
    builder.append(reader.readUTF());
    builder.append(reader.readDouble());
    reader.close();
    System.out.println(builder);
}