lightbulbanalysis.java

Java经典例程 从外国一大学计算机教授出版物下载的代码 经典

import java.io.*;
import javagently.*;
import myutilities.*;

class LightBulbAnalysis {

  /* The light bulb program              J M Bishop 1990, 1998
   * ----------------------              updated May 2000
   *
   *  Calculates the average light of light bulbs
   *  Uses the mean and stddev methods created
   *  in a Stats class in the myutilities package.
   *
   *  Illustrates array i/o again
   */

    LightBulbAnalysis () throws IOException {
      int max = 101;
      Display display = new Display("Light Bulb Analysis");

      display.println ("***** Light Bulb Analysis *****\n");
      display.println ("Statistical analysis of the lifetime of "+
                       "light bulbs");
      display.println("with no. of readings < "+max);
      display.println("Enter in the readings pressing ready after each one");
      display.println("Enter yes for stop with the last reading");
      display.prompt("Hours",0);
      display.prompt("Stop", "no");

      double hourReadings [] = new double[max];
      int n = 0;
      boolean stop = false;

      for (n=1; n<max & !stop; n++) {
        display.ready();
        hourReadings[n] = display.getDouble("Hours");
        display.print(Stream.format(hourReadings[n],6,1)+"  ");
        stop = display.getString("Stop").equalsIgnoreCase("yes");
      }
      n--;
      display.println("\nThat's the data, thanks");
      display.println("There were "+n+" samples");

      if (n == 1) {
        System.out.println("Mean = "+
           Stream.format(Stats.mean(hourReadings,n),10,6)+
           " but standard deviation not defined for n=1");
      }
      else {
        double ave = Stats.mean(hourReadings,n);
        display.println("Mean = "+Stream.format(ave,6,2)+
                           " hours");
        display.println("Standard deviation = " +
           Stream.format(
             Stats.stddev(hourReadings,n,ave),6,2) + " hours");
      }
    }

  public static void main (String [] args) throws IOException {
    new LightBulbAnalysis ();
  }
}