Refactoring step2

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

@@ -4,32 +4,38 @@
  * Represents a pendulum
  */
 public abstract class AbstractPendulum {
-
-
+
     /* 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)
      */
+    public static double gravity = 9.80665;
     private double stringLength, pointMass;
     protected double theta0; 
-    protected double g; 
+    public interface gravityInter {
+    	 public static void GravityConstant(double gra) { 
+    		 gravity = gra; 
+    	}
+		 public static double getGravitationalField() { 
+			 return gravity; 
+		}
+	}
 
     /**
      * Creates a new Pendulum instance using
      * inLength: the string length (>0)
      * inMass: the point mass (>0)
      * inTheta0: angular displacement at t=0 (0<=theta0)
-     * inG: gravitational field value to use
+     * GRAVITY: Always the gravitational field value to use from now on. Replaces inG.
      */
-    public AbstractPendulum (double inLength, double inMass, double inTheta0, double inG) {
+    public AbstractPendulum (double inLength, double inMass, double inTheta0) {
 	if (validStringLength (inLength)) stringLength = inLength;
 	else throw new IllegalArgumentException ("invalid string length: " + inLength);
 	if (validPointMass(inMass)) pointMass = inMass;
 	else throw new IllegalArgumentException ("invalid point mass: " + inMass);
 	if (validDisplacement (inTheta0)) theta0 = inTheta0;
-	else throw new IllegalArgumentException 
-		 ("invalid angular displacement: " + inTheta0);
-	if (validGC (inG)) g = inG;
-	else throw new IllegalArgumentException ("invalid local gravitational field: " + inG);
+	else throw new IllegalArgumentException ("invalid angular displacement: " + inTheta0);
+	if (validGC (gravity)) gravityInter.getGravitationalField();
+	else throw new IllegalArgumentException ("invalid local gravitational field: " + gravity);
     }
 
     private boolean validDisplacement (double val) { return (val >= 0); }
@@ -42,7 +48,6 @@ public AbstractPendulum (double inLength, double inMass, double inTheta0, double
     public double getPointMass () { return pointMass; }
 
     public double getStringLength () { return stringLength; }
-
-    public double getGravitationalField () { return g; }
-
+
+    public double grav = gravityInter.getGravitationalField();//get the grav number in the gravityInter
 }

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

@@ -3,6 +3,7 @@
 import java.text.NumberFormat;
 
 /** 
+ * 
  * compares the values of a simple pendulum using the harmonic motion equation
  * versus the Euler algorithm approximation
  */

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

@@ -1,6 +1,7 @@
 package dal.gravity;
 
 /**
+ * 
  * Represents a pendulum
  */
 public class RegularPendulum extends AbstractEarthPendulum {
@@ -18,7 +19,7 @@ public RegularPendulum (double inLength, double inMass, double inTheta0,
 	dissipation = inDiss;
 	lastVel = 0;
 	lastTheta = this.getMaxAngularDisplacement ();
-	lastAccel = -(this.getGravitationalField () / this.getStringLength ())*Math.sin (lastTheta);
+	lastAccel = -(grav/ this.getStringLength ())*Math.sin (lastTheta);
     }
 
     public RegularPendulum (double inLength, double inMass, double inTheta0, 
@@ -30,7 +31,7 @@ public void step () {
 	iterations++;
 	lastTheta = lastTheta + lastVel*delta;
 	lastVel = lastVel + lastAccel*delta;
-	lastAccel = - dissipation*lastVel - this.getGravitationalField () / this.getStringLength () * Math.sin (lastTheta);
+	lastAccel = - dissipation*lastVel - grav/ this.getStringLength () * Math.sin (lastTheta);
     }
 
     public double getLastTheta () { return lastTheta; }

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

@@ -1,6 +1,7 @@
 package dal.gravity;
 
 /**
+ * 
  * Represents pendulums exhibiting (approximately) simple harmonic motion
  */
 public class SimplePendulum extends AbstractEarthPendulum {
@@ -15,9 +16,9 @@ public class SimplePendulum extends AbstractEarthPendulum {
      */
     public SimplePendulum (double inLength, double inMass, double inTheta0) {
 	super (inLength, inMass, inTheta0);
-	angularFrequency = Math.sqrt (this.getGravitationalField () / this.getStringLength ());
+	angularFrequency = Math.sqrt (grav/ this.getStringLength ());
 	periodOfMotion = 2 * Math.PI 
-	    * Math.sqrt (this.getStringLength () / this.getGravitationalField ());
+	    * Math.sqrt (this.getStringLength () / grav);
     }
 
     /**