Java树形数据（或者说级联）分类

- 这几天做东西时遇到一个树形数据（或者说级联，不会形容了，就这么叫吧）分类的问题，开始有点纠结，后想到了一种方法实现，先分享出来，高手勿喷。

正文开始
现有三个类：分别是Chapter.java Section.java KnowledgePoint.java
Chapter.java
private Set sections = new HashSet(0);
public Set getSections() {
return this.sections;
}

public void setSections(Set sections) {
this.sections = sections;
}
Section.java
private Chapter chapter;
private Set knowledgePoints = new HashSet(0);
public Chapter getChapter() {
return this.chapter;
}

public void setChapter(Chapter chapter) {
this.chapter = chapter;
}
public Set getKnowledgePoints() {
return this.knowledgePoints;
}

public void setKnowledgePoints(Set knowledgePoints) {
this.knowledgePoints = knowledgePoints;
}

KnowledgePoint.java
private Section section;
public Section getSection() {
return this.section;
}

public void setSection(Section section) {
this.section = section;
}

可以看出 章节 有多个小节，小节有多个知识点。当取得知识点后怎么根据不同的章节和小节分类呢？

List kps = this.allService.getKnowledgePointService()
.findPoints(kpIds);//取得所选择的知识点
/** *//********** 根据小节分类知识点 **********/ Map map = new HashMap();
for (int i = 0; i < kps.size(); i++) {
Section section = kps.get(i).getSection();
Integer key = section.getId();
if (!map.containsKey(key)) {
section.getKnowledgePoints().clear();
map.put(key, section);
}
map.get(key).getKnowledgePoints().add(kps.get(i));
}
/** *//********** 根据章节分类小节 **********/
Map cpMap = new HashMap();
Iterator