Java SE (Java Platform, Standard Edition)

I am trying to rotate around the X-Axis and the Y-Axis, but the cube is only rotating around one of them.
Here's my code:

	TransformGroup objSpin = new TransformGroup();
	objSpin.setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE);
                BranchGroup branchgroup = new BranchGroup();
                branchgroup.addChild(transroot);
	transroot.addChild(objSpin);
	objSpin.addChild(new ColorCube(0.12));
	Transform3D yAxis = new Transform3D();
	yAxis.rotY(Math.PI/2.0);
	Transform3D xAxis = new Transform3D();
	xAxis.rotX(Math.PI/2.0);
	Alpha rotationAlpha = new Alpha(-1, 7000);
	Alpha rotationAlphaa = new Alpha(-1, 7000);
	RotationInterpolator rotator =
	    new RotationInterpolator(rotationAlpha, objSpin, yAxis,
				     0.0f, (float) Math.PI*2.0f);
	RotationInterpolator rotatora =
	    new RotationInterpolator(rotationAlphaa, objSpin, xAxis,
				     0.0f, (float) Math.PI*2.0f);
	BoundingSphere bounds = new BoundingSphere();
	BoundingSphere boundsa = new BoundingSphere();
	rotator.setSchedulingBounds(bounds);
	rotatora.setSchedulingBounds(bounds);
	objSpin.addChild(rotator);
	objSpin.addChild(rotatora);

What do I have to do to combine the two RotationInterpolators?