Fix commit from revision 953 which reverted a bunch of changes related to Froyo compatibility.

core/src/net/sf/openrocket/util/LinearInterpolator.java

@@ -1,9 +1,8 @@
 package net.sf.openrocket.util;
 
-import java.util.Arrays;
 import java.util.Iterator;
 import java.util.List;
-import java.util.Map;
+import java.util.SortedMap;
 import java.util.TreeMap;
 
 public class LinearInterpolator implements Cloneable {
@@ -16,7 +15,7 @@ public class LinearInterpolator implements Cloneable {
 	 */
 	public LinearInterpolator() {
 	}
-	
+
 	/**
 	 * Construct a <code>LinearInterpolator</code> with the given points.
 	 * 
@@ -29,11 +28,11 @@ public class LinearInterpolator implements Cloneable {
 	public LinearInterpolator(double[] x, double[] y) {
 		addPoints(x,y);
 	}
-	
+
 	public LinearInterpolator(List<Double> x, List<Double> y) {
 		addPoints(x,y);
 	}
-	
+
 	/**
 	 * Add the point to the linear interpolation.
 	 * 
@@ -43,7 +42,7 @@ public class LinearInterpolator implements Cloneable {
 	public void addPoint(double x, double y) {
 		sortMap.put(x, y);
 	}
-	
+
 	/**
 	 * Add the points to the linear interpolation.
 	 * 
@@ -61,7 +60,7 @@ public class LinearInterpolator implements Cloneable {
 			sortMap.put(x[i],y[i]);
 		}
 	}
-	
+
 	public void addPoints(List<Double> x, List<Double> y){
 		if (x.size() != y.size()) {
 			throw new IllegalArgumentException("Array lengths do not match, x="+x.size() +
@@ -71,40 +70,65 @@ public class LinearInterpolator implements Cloneable {
 			sortMap.put( (Double) x.toArray()[i], (Double) y.toArray()[i]);
 		}
 	}
-	
-	
-	public double getValue(double x) {
-		Map.Entry<Double,Double> e1, e2;
-		double x1, x2;
-		double y1, y2;
-		
-		e1 = sortMap.floorEntry(x);
-		
-		if (e1 == null) {
-			// x smaller than any value in the set
-			e1 = sortMap.firstEntry();
-			if (e1 == null) {
-				throw new IllegalStateException("No points added yet to the interpolator.");
-			}
-			return e1.getValue();
-		}
-		
-		x1 = e1.getKey();
-		e2 = sortMap.higherEntry(x1);
 
-		if (e2 == null) {
-			// x larger than any value in the set
-			return e1.getValue();
+
+	public double getValue(double x) {
+		double x1, x2;
+		Double y1, y2;
+		// Froyo does not support floorEntry, firstEntry or higherEntry.  We instead have to
+		// resort to using other more awkward methods.
+
+		y1 = sortMap.get(x);
+
+		if ( y1 != null ) {
+			// Wow, x was a key in the map.  Such luck.
+			return y1.doubleValue();
+		}
+
+		// we now know that x is not in the map, so we need to find the lower and higher keys.
+		
+		// let's just make certain that our map is not empty.
+		if ( sortMap.isEmpty() ) {
+			throw new IllegalStateException("No points added yet to the interpolator.");
 		}
 		
-		x2 = e2.getKey();
-		y1 = e1.getValue();
-		y2 = e2.getValue();
+		// firstKey in the map - cannot be null since the map is not empty.
+		Double firstKey = sortMap.firstKey();
+
+		// x is smaller than the first entry in the map.
+		if ( x < firstKey.doubleValue() ) {
+			y1 = sortMap.get(firstKey);
+			return y1.doubleValue();
+		}
 		
+		// floor key is the largest key smaller than x - since we have at least one key,
+		// and x>=firstKey, we know that floorKey != null.
+		Double floorKey = sortMap.subMap(firstKey, x).lastKey();
+
+		x1 = floorKey.doubleValue();
+		y1 = sortMap.get(floorKey);
+
+		// Now we need to find the key that is greater or equal to x
+		SortedMap<Double,Double> tailMap = sortMap.tailMap(x);
+
+		// Check if x is bigger than all the entries.
+		if ( tailMap.isEmpty() ) {
+			return y1.doubleValue();
+		}
+		Double ceilKey = tailMap.firstKey();
+		
+		// Check if x is bigger than all the entries.
+		if ( ceilKey == null ) {
+			return y1.doubleValue();
+		}
+		
+		x2 = ceilKey.doubleValue();
+		y2 = sortMap.get(ceilKey);
+
 		return (x - x1)/(x2-x1) * (y2-y1) + y1;
 	}
-	
-	
+
+
 	public double[] getXPoints() {
 		double[] x = new double[sortMap.size()];
 		Iterator<Double> iter = sortMap.keySet().iterator();
@@ -113,8 +137,8 @@ public class LinearInterpolator implements Cloneable {
 		}
 		return x;
 	}
-	
-	
+
+
 	@SuppressWarnings("unchecked")
 	@Override
 	public LinearInterpolator clone() {
@@ -127,25 +151,4 @@ public class LinearInterpolator implements Cloneable {
 		}
 	}
 
-	
-	public static void main(String[] args) {
-		LinearInterpolator interpolator = new LinearInterpolator(
-				new double[] {1, 1.5, 2, 4, 5},
-				new double[] {0, 1,   0, 2, 2}
-		);
-		
-		for (double x=0; x < 6; x+=0.1) {
-			System.out.printf("%.1f:  %.2f\n", x, interpolator.getValue(x));
-		}
-		
-		// Should be the same
-		
-		ArrayList<Double> time = new ArrayList<Double>( Arrays.asList( new Double[] {1.0, 1.5, 2.0, 4.0, 5.0} ));
-		ArrayList<Double> y = new ArrayList<Double>( Arrays.asList( new Double[] {0.0, 1.0, 0.0, 2.0, 2.0} ));
-		
-		LinearInterpolator interpolator2 = new LinearInterpolator(time,y);
-		for (double x=0; x < 6; x+=0.1) {
-			System.out.printf("%.1f:  %.2f\n", x, interpolator2.getValue(x));
-		}
-	}	
 }