Java3D与Eclipse的环境搭建问题，顺利安装JDK，Eclipse，java3d，并编了一个小程序 出错如下：

Exception in thread "main" java.lang.Error: Unresolved compilation problems:
Access restriction: The type BranchGroup is not accessible due to restriction on required library C:\Program Files\Java\jdk1.6.0\jre\lib\ext\j3dcore.jar
Access restriction: The constructor BranchGroup() is not accessible due to restriction on required library C:\Program Files\Java\jdk1.6.0\jre\lib\ext\j3dcore.jar
Access restriction: The type BranchGroup is not accessible due to restriction on required library C:\Program Files\Java\jdk1.6.0\jre\lib\ext\j3dcore.jar
Access restriction: The type Transform3D is not accessible due to restriction on required library C:\Program Files\Java\jdk1.6.0\jre\lib\ext\j3dcore.jar
Access restriction: The constructor Transform3D() is not accessible due to restriction on required library C:\Program Files\Java\jdk1.6.0\jre\lib\ext\j3dcore.jar
Access restriction: The type Transform3D is not accessible due to restriction on required library C:\Program Files\Java\jdk1.6.0\jre\lib\ext\j3dcore.jar
Access restriction: The type Transform3D is not accessible due to restriction on required library C:\Program Files\Java\jdk1.6.0\jre\lib\ext\j3dcore.jar
Access restriction: The constructor Transform3D() is not accessible due to restriction on required library C:\Program Files\Java\jdk1.6.0\jre\lib\ext\j3dcore.jar
Access restriction: The type Transform3D is not accessible due to restriction on required library C:\Program Files\Java\jdk1.6.0\jre\lib\ext\j3dcore.jar
Access restriction: The method rotY(double) from the type Transform3D is not accessible due to restriction on required library C:\Program Files\Java\jdk1.6.0\jre\lib\ext\j3dcore.jar
Access restriction: The method rotX(double) from the type Transform3D is not accessible due to restriction on required library C:\Program Files\Java\jdk1.6.0\jre\lib\ext\j3dcore.jar
Access restriction: The method mul(Transform3D) from the type Transform3D is not accessible due to restriction on required library C:\Program Files\Java\jdk1.6.0\jre\lib\ext\j3dcore.jar
Access restriction: The method setRotation(AxisAngle4d) from the type Transform3D is not accessible due to restriction on required library C:\Program Files\Java\jdk1.6.0\jre\lib\ext\j3dcore.jar
Access restriction: The constructor AxisAngle4d(double, double, double, double) is not accessible due to restriction on required library C:\Program Files\Java\jdk1.6.0\jre\lib\ext\vecmath.jar
Access restriction: The type AxisAngle4d is not accessible due to restriction on required library C:\Program Files\Java\jdk1.6.0\jre\lib\ext\vecmath.jar
Access restriction: The method setScale(Vector3d) from the type Transform3D is not accessible due to restriction on required library C:\Program Files\Java\jdk1.6.0\jre\lib\ext\j3dcore.jar