Fixing build issues.

Author: the-yash-rajput

src/main/java/com/thealgorithms/physics/ElasticCollision2D.java

@@ -1,15 +1,24 @@
 package com.thealgorithms.physics;
 
+/**
+ * 2D Elastic collision between two circular bodies
+ * Based on principles of conservation of momentum and kinetic energy.
+ *
+ * @author [Yash Rajput](https://github.com/the-yash-rajput)
+ */
 public final class ElasticCollision2D {
 
     private ElasticCollision2D() {
-        // utility class
+        throw new AssertionError("No instances. Utility class");
     }
 
     public static class Body {
-        public double x, y;
-        public double vx, vy;
-        public double mass, radius;
+        public double x;
+        public double y;
+        public double vx;
+        public double vy;
+        public double mass;
+        public double radius;
 
         public Body(double x, double y, double vx, double vy, double mass, double radius) {
             this.x = x;
@@ -31,22 +40,28 @@ public static void resolveCollision(Body a, Body b) {
         double dx = b.x - a.x;
         double dy = b.y - a.y;
         double dist = Math.hypot(dx, dy);
-        if (dist == 0) return; // overlapping
+
+        if (dist == 0) {
+            return; // overlapping
+        }
 
         double nx = dx / dist;
         double ny = dy / dist;
 
         // relative velocity along normal
         double rv = (b.vx - a.vx) * nx + (b.vy - a.vy) * ny;
-        if (rv > 0) return; // moving apart
 
-        // Correct 2D impulse with masses
+        if (rv > 0) {
+            return; // moving apart
+        }
+
+        // impulse with masses
         double m1 = a.mass;
         double m2 = b.mass;
 
         double j = -(1 + 1.0) * rv / (1.0 / m1 + 1.0 / m2);
 
-        // impulse vector along normal
+        // impulse vector
         double impulseX = j * nx;
         double impulseY = j * ny;