Refactoring Step 1

src/main/java/dal/gravity/AbstractPendulum.java

@@ -5,8 +5,10 @@
  */
 public abstract class AbstractPendulum {
 
-
-    /* instance variables - string length, point mass, angular displacement
+//abstract class
+    /** gravitational constant */
+	public static final double GRAVITY = 9.80665;
+	/* instance variables - string length, point mass, angular displacement
      * at t=0, constant for local gravitational field in m/s^2 (e.g., 9.81 on Earth)
      */
     private double stringLength, pointMass;

src/main/java/dal/gravity/PendulumRunner.java

@@ -7,7 +7,7 @@
  * versus the Euler algorithm approximation
  */
 public class PendulumRunner {
-
+//run the main
     public static void main (String [] args) {
 	NumberFormat nf = NumberFormat.getInstance ();
 	nf.setMaximumFractionDigits (3);

src/main/java/dal/gravity/RegularPendulum.java

@@ -3,7 +3,7 @@
 /**
  * Represents a pendulum
  */
-public class RegularPendulum extends AbstractEarthPendulum {
+public class RegularPendulum extends AbstractPendulum {
     private double delta, iterations = 0;
     private double dissipation;
     private double lastTheta, lastVel, lastAccel;
@@ -13,7 +13,7 @@ public class RegularPendulum extends AbstractEarthPendulum {
      */
     public RegularPendulum (double inLength, double inMass, double inTheta0, 
 		     double inDelta, double inDiss) {
-	super (inLength, inMass, inTheta0);
+	super (inLength, inMass, inTheta0, GRAVITY);
 	delta=inDelta;
 	dissipation = inDiss;
 	lastVel = 0;
@@ -25,7 +25,7 @@ public RegularPendulum (double inLength, double inMass, double inTheta0,
 		     double inDelta) {
 	this (inLength, inMass, inTheta0, inDelta, 0);
     }
-
+   
     public void step () {
 	iterations++;
 	lastTheta = lastTheta + lastVel*delta;

src/main/java/dal/gravity/SimplePendulum.java

@@ -3,18 +3,18 @@
 /**
  * Represents pendulums exhibiting (approximately) simple harmonic motion
  */
-public class SimplePendulum extends AbstractEarthPendulum {
+public class SimplePendulum extends AbstractPendulum {
 
     private double angularFrequency, periodOfMotion;
-
+//simple
     /**
      * Creates a new Pendulum instance using
      * inLength: the string length (>0)
      * inMass: the point mass (>0)
      * inTheta0: angular displacement at t=0 (0<=theta0<=pi/6)
      */
     public SimplePendulum (double inLength, double inMass, double inTheta0) {
-	super (inLength, inMass, inTheta0);
+	super (inLength, inMass, inTheta0,GRAVITY);
 	angularFrequency = Math.sqrt (this.getGravitationalField () / this.getStringLength ());
 	periodOfMotion = 2 * Math.PI 
 	    * Math.sqrt (this.getStringLength () / this.getGravitationalField ());