RVec3Arg: add 3 methods

src/main/java/com/github/stephengold/joltjni/RVec3.java

@@ -272,6 +272,47 @@ public Object getZ() {
         return result;
     }
 
+    /**
+     * Test whether the squared length is within 1e-12 (single-precision) or
+     * 1e-24 (double-precision) of zero. The vector is unaffected.
+     *
+     * @return {@code true} if nearly zero, otherwise {@code false}
+     */
+    @Override
+    public boolean isNearZero() {
+        double tolerance = Jolt.isDoublePrecision() ? 1e-24 : 1e-12;
+        boolean result = isNearZero(tolerance);
+        return result;
+    }
+
+    /**
+     * Test whether the squared length is within the specified tolerance of
+     * zero. The vector is unaffected.
+     *
+     * @param tolerance the desired tolerance (≥0)
+     * @return {@code true} if nearly zero, otherwise {@code false}
+     */
+    @Override
+    public boolean isNearZero(double tolerance) {
+        double lengthSq = lengthSq();
+        if (lengthSq <= tolerance) {
+            return true;
+        } else {
+            return false;
+        }
+    }
+
+    /**
+     * Return the squared length. The vector is unaffected.
+     *
+     * @return the squared length
+     */
+    @Override
+    public double lengthSq() {
+        double result = xx * xx + yy * yy + zz * zz;
+        return result;
+    }
+
     /**
      * Copy the components to an array. The vector is unaffected.
      *

src/main/java/com/github/stephengold/joltjni/readonly/RVec3Arg.java

@@ -67,6 +67,30 @@ public interface RVec3Arg {
      */
     Object getZ();
 
+    /**
+     * Test whether the squared length is within 1e-12 (single-precision) or
+     * 1e-24 (double-precision) of zero. The vector is unaffected.
+     *
+     * @return {@code true} if nearly zero, otherwise {@code false}
+     */
+    boolean isNearZero();
+
+    /**
+     * Test whether the squared length is within the specified tolerance of
+     * zero. The vector is unaffected.
+     *
+     * @param tolerance the desired tolerance (&gel0)
+     * @return {@code true} if nearly zero, otherwise {@code false}
+     */
+    boolean isNearZero(double tolerance);
+
+    /**
+     * Return the squared length. The vector is unaffected.
+     *
+     * @return the squared length
+     */
+    double lengthSq();
+
     /**
      * Copy the components to an array. The vector is unaffected.
      *