Homework Assignment 5

Due: 9am, December 8, 2008.

This assignment will give you practice at writing Java program that contain:

Solve problems 34, 35 and 37 in the Java Programming Exercises + the egg mesh problem below.

Graphical Display and Engineering Property Calculation for Egg Mesh

The adjacent figure shows a screendump of an egg mesh.

Figure. Screendump of egg mesh.

The left-hand side of the mesh is essentially a wheel, with constant inside and outside diameters. The right-hand side of the mesh is a composition of two shapes. The inner boundary is a circle. The outer boundary is an ellipse. The left and right-hand sides have compatible dimensions. The red dot shows the position of the centroid.

To get started:

Things to do:

Points to note:

  1. For problems 34 and 35 you can work directly from the material given in the "blue" class reader.
  2. For problem 37, you can download the "data array" source code from the java examples web page. The first-cut version of the rainfall analysis program is as follows: 
    /*
 *  =============================================================
 *  RainfallAnalysis.java: The java program conducts a simple 
 *  statistical analysis on monthly rainfall measurements.
 *
 *  Written By: Mark Austin                         November 2005
 *  =============================================================
 */

import java.lang.Math;

public class RainfallAnalysis {

   // No of columns in print array task...

   public final static int NoColumns = 6;

   // =========================================================
   // main method : this is where the program execution begins.
   // =========================================================

   public static void main ( String [] args ) {

       // [a] Populate rainfall data array (measured over 30 days)

       float [] fRainfall = {  1.1F, 0.8F, 1.1F, 1.2F, 0.5F, 0.2F,
                              0.05F, 0.0F, 0.0F, 0.0F, 0.4F, 0.5F,
                               0.6F, 0.8F, 1.0F, 1.2F, 3.0F, 2.4F,
                               1.5F, 1.0F, 1.0F, 0.0F, 0.0F, 0.0F,
                               0.0F, 0.0F, 0.0F, 2.0F, 2.0F, 2.4F };

       // [b] Print contents of fRainfall in six columns ...

       System.out.println("Array: fRainfall");
       System.out.println("----------------");
       for (int i = 1; i <= fRainfall.length; i = i + 1) {
            System.out.printf( " %4.2f", fRainfall [i-1] );
            if (i % NoColumns == 0 || i == fRainfall.length ) 
                System.out.println("");
       }
       System.out.println("----------------");

       // [b] Compute and print rainfall measurement statistics..

       System.out.println("");
       System.out.println("Statistics of Daily Rainfall");
       System.out.println("============================");

       System.out.printf("Max value = %5.2f\n", maxValue( fRainfall ));
       System.out.printf("Min value = %5.2f\n", minValue( fRainfall ));
       System.out.printf("Range of values = %5.2f\n", range( fRainfall ));
       System.out.printf("Mean value = %5.2f\n", mean( fRainfall ));
       System.out.printf("Standard deviation = %5.2f\n", std( fRainfall ));
       System.out.println("============================");
   }

   /* ================================================== */
   /* Methods to compute maximum/minimum daily rainfalls */
   /* ================================================== */

   public static float maxValue ( float fA [] ) {
      float fMax = fA[0];

      for (int i = 0; i < fA.length; i = i + 1)
         fMax = Math.max( fMax, fA [i] );

      return fMax;
   }

   public static float minValue ( float fA [] ) {
      float fMin = fA[0];

      for (int i = 0; i < fA.length; i = i + 1)
         fMin = Math.min( fMin, fA [i] );

      return fMin;
   }

   /* ========================================== */
   /* Method to compute range in daily rainfalls */
   /* ========================================== */

   public static float range ( float fA [] ) {
      return ( maxValue (fA) - minValue(fA) );
   }

   /* ====================================================== */
   /* Compute mean and standard deviation of daily rainfalls */
   /* ====================================================== */

   public static float mean ( float fA [] ) {
      float fSum = 0.0F;

      for (int i = 0; i < fA.length; i = i + 1)
         fSum = fSum + fA[i];

      return fSum/fA.length;
   }

   public static float std ( float fA [] ) {
      float fMean = mean ( fA );

      float fSum = 0.0F;
      for (int i = 0; i < fA.length; i = i + 1)
         fSum = fSum + fA[i]*fA[i];

      return (float) Math.sqrt(fSum/fA.length - fMean*fMean);
   }
}

    You should find that the data array version of the rainfall analysis is much shorter!!

Note. For each problem, hand in a copy of your program source code and a script of I/O for typical program usage.

If you are working on UNIX/Mac OS X then the procedure for creating a script is easy -- just type something like: 

    prompt >> script output-file

Now all input/output on the screen will be echoed to the file "output-file". To terminate the script, type: 

    prompt >> exit

Now print "output-file" and hand it in.

If you are working on Windows, just cut-and-paste the output into a Word document.

Developed in October 2008 by Mark Austin
Copyright © 2008, Department of Civil and Environmental Engineering, University of Maryland