### Question:
Transform { public Transform multiply(Transform other) { return new Transform(apply(other.translation), apply(other.rotationAndScale)); } Transform(Vector3 translation, Quaternion rotation); static Transform fromTransformMessage(geometry_msgs.Transform message); static Transform fromPoseMessage(geometry_msgs.Pose message); static Transform identity(); static Transform xRotation(double angle); static Transform yRotation(double angle); static Transform zRotation(double angle); static Transform translation(double x, double y, double z); static Transform translation(Vector3 vector); Transform multiply(Transform other); Transform invert(); Vector3 apply(Vector3 vector); Quaternion apply(Quaternion quaternion); Transform scale(double factor); double getScale(); double[] toMatrix(); geometry_msgs.Transform toTransformMessage(geometry_msgs.Transform result); geometry_msgs.Pose toPoseMessage(geometry_msgs.Pose result); geometry_msgs.PoseStamped toPoseStampedMessage(GraphName frame, Time stamp,
      geometry_msgs.PoseStamped result); boolean almostEquals(Transform other, double epsilon); @Override String toString(); @Override int hashCode(); @Override boolean equals(Object obj);  }### Answer:
@Test public void testMultiply() { Transform transform1 = new Transform(Vector3.xAxis(), Quaternion.identity()); Transform transform2 = new Transform(Vector3.yAxis(), Quaternion.fromAxisAngle(Vector3.zAxis(), Math.PI / 2)); Transform result1 = transform1.multiply(transform2); assertEquals(1.0, result1.getTranslation().getX(), 1e-9); assertEquals(1.0, result1.getTranslation().getY(), 1e-9); assertEquals(0.0, result1.getTranslation().getZ(), 1e-9); assertEquals(0.0, result1.getRotationAndScale().getX(), 1e-9); assertEquals(0.0, result1.getRotationAndScale().getY(), 1e-9); assertEquals(0.7071067811865475, result1.getRotationAndScale().getZ(), 1e-9); assertEquals(0.7071067811865475, result1.getRotationAndScale().getW(), 1e-9); Transform result2 = transform2.multiply(transform1); assertEquals(0.0, result2.getTranslation().getX(), 1e-9); assertEquals(2.0, result2.getTranslation().getY(), 1e-9); assertEquals(0.0, result2.getTranslation().getZ(), 1e-9); assertEquals(0.0, result2.getRotationAndScale().getX(), 1e-9); assertEquals(0.0, result2.getRotationAndScale().getY(), 1e-9); assertEquals(0.7071067811865475, result2.getRotationAndScale().getZ(), 1e-9); assertEquals(0.7071067811865475, result2.getRotationAndScale().getW(), 1e-9); }