Java 3D Desktop Environment旨在使用Java 3D来创建一个3D桌面环境。功能包括：分布式的应用程序

				package org.j3de.ui.constraint;								import javax.media.j3d.BoundingBox;								import javax.vecmath.Vector3d;   				import javax.vecmath.Point3d;   								import org.w3c.dom.Node;				import org.w3c.dom.Document;     				import org.w3c.dom.Element;								import org.j3de.ui.LayoutConstraint;				import org.j3de.ui.LayoutInfo;				import org.j3de.ui.UIElement;				import org.j3de.ui.WrongParameterException;				import org.j3de.util.AbstractComponent;				import org.j3de.util.StringParser;				import org.j3de.util.ConfigurationException;								public class RelativPositionConstraint extends AbstractComponent implements LayoutConstraint  {				  private LayoutInfo layoutInfo;				  private UIElement  element1;				  private UIElement  element2;								  private Vector3d   referencePoint1;				  private Vector3d   referencePoint2;				  private Vector3d   relativPosition;				 				  public void             setLayoutInfo(LayoutInfo layoutInfo) {				    this.layoutInfo = layoutInfo;				  }  								  public boolean          appliesTo(UIElement element) {				    return element.equals(element2);				  }								  private Vector3d getPosition(Vector3d referencePoint, UIElement element) {				    BoundingBox bb = new BoundingBox(layoutInfo.getBounds(element));				    Point3d upper = new Point3d();				    Point3d lower = new Point3d();								    bb.getUpper(upper);				    bb.getLower(lower);								    double x = lower.x + (upper.x - lower.x) * referencePoint.x; 				    double y = lower.y + (upper.y - lower.y) * referencePoint.y; 				    double z = lower.z + (upper.z - lower.z) * referencePoint.z; 								    return new Vector3d(x, y, z);				  }								  public void             getForce(Vector3d force) {				    Vector3d point1 = getPosition(referencePoint1,  element1);				    Vector3d point2 = getPosition(referencePoint2,  element2);				 				    Vector3d position1 = new Vector3d();				    Vector3d position2 = new Vector3d();								    layoutInfo.getPosition(element1, position1);				    layoutInfo.getPosition(element2, position2);				 				    point1.add(position1);				    point2.add(position2);								    force.set(point2);				    force.sub(point1);				    force.sub(relativPosition);				  }				  				  public boolean removeReferencesTo(UIElement element) {				    if (element1 == element) 				      return true;								    if (element2 == element) 				      return true;				    				    return false;				  }				   				  public void setParam(ConstraintParam param) throws WrongParameterException {				    if (!(param instanceof TwoElementConstraintParam))				      throw new WrongParameterException(this.getClass(), TwoElementConstraintParam.class, param.getClass());								    element1 = ((TwoElementConstraintParam)param).getElement1();				    element2 = ((TwoElementConstraintParam)param).getElement2();				  }								  public LayoutConstraint cloneConstraint() {				    RelativPositionConstraint constraint = new  RelativPositionConstraint();				    constraint.referencePoint1 = this.referencePoint1;				    constraint.referencePoint2 = this.referencePoint2;				    constraint.relativPosition = this.relativPosition;				    return constraint;				  }								  public void configure(Node node, Document nodeFactory) throws ConfigurationException {       				    super.configure(node, nodeFactory);   								    referencePoint1 = StringParser.parseVector3d(helper.getPropertyValue("referencePoint1", "0.0 0.0 0.0", true));				    referencePoint2 = StringParser.parseVector3d(helper.getPropertyValue("referencePoint2", "0.0 0.0 0.0", true));				    relativPosition = StringParser.parseVector3d(helper.getPropertyValue("relativPosition", "0.0 0.0 0.0", true));				  }								}