Data commit

Task/Roots-of-a-function/Java/roots-of-a-function.java

@@ -0,0 +1,38 @@
+public class Roots {
+    public interface Function {
+	public double f(double x);
+    }
+
+    private static int sign(double x) {
+	return (x < 0.0) ? -1 : (x > 0.0) ? 1 : 0;
+    }
+
+    public static void printRoots(Function f, double lowerBound,
+				  double upperBound, double step) {
+	double x = lowerBound, ox = x;
+	double y = f.f(x), oy = y;
+	int s = sign(y), os = s;
+
+	for (; x <= upperBound ; x += step) {
+	    s = sign(y = f.f(x));
+	    if (s == 0) {
+		System.out.println(x);
+	    } else if (s != os) {
+		double dx = x - ox;
+		double dy = y - oy;
+		double cx = x - dx * (y / dy);
+		System.out.println("~" + cx);
+	    }
+	    ox = x; oy = y; os = s;
+	}
+    }
+
+    public static void main(String[] args) {
+	Function poly = new Function () {
+	    public double f(double x) {
+		return x*x*x - 3*x*x + 2*x;
+	    }
+	};
+	printRoots(poly, -1.0, 4, 0.002);
+    }
+}