Use DataInputStream to create double : DataInputStream « File « Java Tutorial

1. Java Tutorial
2. File
3. DataInputStream

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();
  }
}