Stephandler methods added to ThreeBodyAPL, began trying to figure out

how to integrate the derivatives. there's a few comments that I
unchecked to show the outputs of energy, center of mass, and the
derivatives. Also, this does return a graph, but no changes are observed
in the plot, so it results in one dot.

src/jat/examples/ThreeBodyExample/ThreeBodyAPL.java

@@ -2,10 +2,13 @@
 
 import java.util.ArrayList;
 
+import org.apache.commons.math3.geometry.euclidean.threed.Vector3D;
 import org.apache.commons.math3.ode.FirstOrderDifferentialEquations;
 import org.apache.commons.math3.ode.sampling.StepHandler;
 import org.apache.commons.math3.ode.sampling.StepInterpolator;
 
+import jat.coreNOSA.algorithm.integrators.Printable;
+import jat.coreNOSA.cm.Constants;
 import jat.coreNOSA.cm.ThreeBody;
 import jat.coreNOSA.math.MatrixVector.data.VectorN;
 
@@ -14,14 +17,15 @@ public class ThreeBodyAPL extends ThreeBody implements FirstOrderDifferentialEqu
 	public ArrayList<Double> xsol = new ArrayList<Double>();
 	public ArrayList<Double> ysol = new ArrayList<Double>();
 	public ArrayList<Double> zsol = new ArrayList<Double>();
+
 	public ThreeBodyAPL(double G, double m1, double m2, double m3) {
 		super(G, m1, m2, m3);
 	}
 
 	@Override
-	public void computeDerivatives(double arg0, double[] arg1, double[] arg2) {
-		// TODO Auto-generated method stub
-
+	public void computeDerivatives(double t, double[] y, double[] yDot) {
+		// returns the derivatives of the ThreeBody problem
+		yDot = this.derivs(t, y);
 	}
 
 	@Override
@@ -30,6 +34,13 @@ public int getDimension() {
 		return 18;
 	}
 	public double[] randv() {
+		// returns the position and velocity of the three objects
+		// vector r1 is x[0], x[1], x[2]
+		// vector v1 is x[3], x[4], x[5]
+		// vector r2 is x[6], x[7], x[8]
+		// vector v2 is x[9], x[10], x[11]
+		// vector r3 is x[12], x[13], x[14]
+		// vector v3 is x[15], x[16], x[17]
 		double[] randv = new double[18];
 		randv[0] = 2.0;
 		randv[1] = 6.0;
@@ -51,19 +62,20 @@ public double[] randv() {
 		randv[17] = 8.0;
 		return randv;
 	}
-	
+
 	public StepHandler stepHandler = new StepHandler() {
 		public void init(double t0, double[] y0, double t) {
 		}
 
 		public void handleStep(StepInterpolator interpolator, boolean isLast) {
 			double t = interpolator.getCurrentTime();
 			double[] y = interpolator.getInterpolatedState();
-			// System.out.println(t + " " + y[0] + " " + y[1]+ " " + y[2]);
+			System.out.println(t + " " + y[0] + " " + y[1]+ " " + y[2]);
 			time.add(t);
 			xsol.add(y[0]);
 			ysol.add(y[1]);
 			zsol.add(y[2]);
 		}
 	};
-}
+
+}

src/jat/examples/ThreeBodyExample/ThreeBodyExample.java

@@ -31,10 +31,10 @@ public static void main(String[] args) {
 		//initialize variables
 		double totalEnergy = 0;
 		// set the final time = one orbit period
-		double tf = 7.0;
+		double tf = 1.0;
 
 		// create a ThreeBody orbit using three masses and gravitational con
-		ThreeBodyAPL sat = new ThreeBodyAPL(10, 0.3, 1.0, 2.0);
+		ThreeBodyAPL sat = new ThreeBodyAPL(9.87, 0.3, 1.0, 2.0);
 		//initialize VectorN elements
 		double[] y = sat.randv();
 
@@ -71,7 +71,7 @@ public static void main(String[] args) {
 
 		double[][] XY = new double[timeArray.length][2];
 
-		// int a=0;
+		 int a=0;
 		// System.arraycopy(timeArray,0,XY[a],0,timeArray.length);
 		// System.arraycopy(ysolArray,0,XY[1],0,ysolArray.length);