QuatArg: add the isZero() method

Author: stephengold

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

@@ -354,6 +354,17 @@ public boolean isNormalized(float tolerance) {
         }
     }
 
+    /**
+     * Test whether the quaternion is zero. The quaternion is unaffected.
+     *
+     * @return {@code true} if exactly zero, otherwise {@code false}
+     */
+    @Override
+    public boolean isZero() {
+        boolean result = (w == 0f) && (x == 0f) && (y == 0f) && (z == 0f);
+        return result;
+    }
+
     /**
      * Return the length. The quaternion is unaffected.
      *

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

@@ -1,5 +1,5 @@
 /*
-Copyright (c) 2024 Stephen Gold
+Copyright (c) 2024-2025 Stephen Gold
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
@@ -90,6 +90,13 @@ public interface QuatArg {
      */
     boolean isNormalized(float tolerance);
 
+    /**
+     * Test whether the quaternion is zero. The quaternion is unaffected.
+     *
+     * @return {@code true} if zero, otherwise {@code false}
+     */
+    boolean isZero();
+
     /**
      * Return the length. The quaternion is unaffected.
      *