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;                                      
				
				import java.io.Serializable;
				
				import javax.vecmath.Vector3d;   
				
				import org.j3de.ui.UIElement;
				import org.j3de.ui.constraint.ConstraintParam;
				
				public interface LayoutConstraint {   
				  public void             setLayoutInfo(LayoutInfo layoutInfo); 
				  public boolean          appliesTo(UIElement element);
				  public void             getForce(Vector3d force);   
				  
				  /** Removes all references to element.
				   * @return if the constraint is unnecesairy after removing element.
				   */
				  public boolean          removeReferencesTo(UIElement element);   
				  public void             setParam(ConstraintParam param) throws WrongParameterException;
				  public LayoutConstraint cloneConstraint();
				}