数据库表中存放着节点信息，表结构为：id 为节点id，name为节点名字，pid为其父节点，如果pid为0则表示此节点为根节点。根据表中数据信息生成一个数对象，里面存放节点的树状信息。
代码如下:
//节点对象
public class Person {
private String id;
private String pid;
private String name;
getter …
setter …
}
// 树根对象，里面级联存储子节点信息，直到树叶
public class TreeObj {
private String id;
private String name;
private List<TreeObj > cList =new ArrayList<TreeObj>();
getter …
setter …
}
public class Test {
public static void main(String[] argStrings) {
List<Person> pList = new ArrayList<Person>();
pList.add(createPerson("1", "0", "a"));
pList.add(createPerson("2", "0", "b"));
pList.add(createPerson("3", "2", "c"));
pList.add(createPerson("4", "2", "d"));
pList.add(createPerson("5", "0", "e"));
pList.add(createPerson("6", "5", "f"));
pList.add(createPerson("7", "6", "g"));
List<TreeObj> treeList = new ArrayList<TreeObj>();
for (Person person : pList) {
// find root note
if ("0".equals(person.getPid())) {
TreeObj treeObj = new TreeObj();
treeObj.setId(person.getId());
treeObj.setName(person.getName());
treeList.add(putObjIterater(pList,treeObj));
}
}
System.out.println(treeList);
}
private static Person createPerson(String id, String pid,String name) {
Person p1 = new Person();
p1.setId(id);
p1.setPid(pid);
p1.setName(name);
return p1;
}
private static TreeObj putObjIterater(List<Person> pList, TreeObj treeObj) {
// find child notes from pList and and the list in treeObj
for (Person person : pList) {
if (treeObj.getId().equals(person.getPid())) {
// if treeObj has child note ,add it to the treeObj's list
TreeObj newTreeObj = new TreeObj();
newTreeObj.setId(person.getId());
newTreeObj.setName(person.getName());
treeObj.getCList().add(newTreeObj);
putObjIterater(pList, newTreeObj);
}
}
return treeObj;
}
}
打印出的treeList就是我们要得到的树对象。