感谢您的建议。
我终于重新发明了轮子……我编写了一个用于持有关联的通用类。我使用两张同步的地图。
协会持有人提供以下方法
void setAssociation(LeftClass left, RightClass right, AssociationClass assoc);AssociationClass getAssociation(LeftClass left, RightClass right);Map<RightClass, AssociationClass> getAssocationsLeft(LeftClass left);Map<LeftClass, AssociationClass> getAssocationsRight(RightClass right); void removeAssociation(LeftClass left, RightClass right);
这是代码：
import java.util.HashMap;public class AssociationHolder<LeftClass, RightClass, AssociationClass> { // ------------------------------------------------------- // Attributes // ------------------------------------------------------- private HashMap<LeftClass, HashMap<RightClass, AssociationClass>> associationsLeft = new HashMap<LeftClass, HashMap<RightClass,AssociationClass>>(); private HashMap<RightClass, HashMap<LeftClass, AssociationClass>> associationsRight = new HashMap<RightClass, HashMap<LeftClass,AssociationClass>>(); // ------------------------------------------------------- // Methods // ------------------------------------------------------- public void setAssociation(LeftClass left, RightClass right, AssociationClass association) { // Get the map for the left HashMap<RightClass, AssociationClass> leftMap = this.associationsLeft.get(left); // No association defined yet for this left key ? => Create new map if (leftMap == null) { leftMap = new HashMap<RightClass, AssociationClass>(); this.associationsLeft.put(left, leftMap); } // Get the map for the right HashMap<LeftClass, AssociationClass> rightMap = this.associationsRight.get(right); // No association defined yet for this right key ? => Create new map if (rightMap == null) { rightMap = new HashMap<LeftClass, AssociationClass>(); this.associationsRight.put(right, rightMap); } // Set the assoication on both maps leftMap.put(right, association); rightMap.put(left, association); } public AssociationClass getAssociation(LeftClass left, RightClass right) { // Use left maps (could have used the right one as well) HashMap<RightClass, AssociationClass> leftMap = this.associationsLeft.get(left); if (leftMap == null) return null; return leftMap.get(right); } public HashMap<RightClass, AssociationClass> getAssociationsLeft(LeftClass left) { HashMap<RightClass, AssociationClass> leftMap = this.associationsLeft.get(left); // No map defined ? return empty one instead of null if (leftMap == null) { return new HashMap<RightClass, AssociationClass>(); } else { return leftMap; } } public HashMap<LeftClass, AssociationClass> getAssociationsRight(RightClass right) { HashMap<LeftClass, AssociationClass> rightMap = this.associationsRight.get(right); // No map defined ? return empty one instead of null if (rightMap == null) { return new HashMap<LeftClass, AssociationClass>(); } else { return rightMap; } } public void removeAssociation(LeftClass left, RightClass right) { HashMap<RightClass, AssociationClass> leftMap = this.getAssociationsLeft(left); HashMap<LeftClass, AssociationClass> rightMap = this.getAssociationsRight(right); leftMap.remove(right); rightMap.remove(left); }}我希望这可以在将来对某人有所帮助。
