Add @Override to toString

src/Vector3.java

@@ -97,6 +97,7 @@ public class Vector3 {
      * Returns the coordinates of this vector in brackets as a string
      * in the form "[x,y,z]", e.g., "[1.48E11,0.0,0.0]".
      */
+    @Override
     public String toString() {
         return String.format("[%g,%g,%g]", x, y, z);
     }