部门实体类：
package mianshi.算法.递归算法.组织树;

import java.util.ArrayList;
import java.util.List;

public class Dept {
private Integer id;
private Integer parentId;
private List<Dept> children = new ArrayList<Dept>();

public Integer getId() {
	return id;
}
public void setId(Integer id) {
	this.id = id;
}
public Integer getParentId() {
	return parentId;
}
public void setParentId(Integer parentId) {
	this.parentId = parentId;
}
public List<Dept> getChildren() {
	return children;
}
public void setChildren(List<Dept> children) {
	this.children = children;
}

@Override
public String toString() {
	return "Dept [id=" + id + ", parentId=" + parentId + ", children="
			+ children + "]";
}

}

遍历树：
package mianshi.算法.递归算法.组织树;

import java.util.ArrayList;
import java.util.List;

public class DeptTest {
private static Dept root;
private static List<Dept> dataBaseList;

public static void main(String[] args) {
	dataBaseList = new ArrayList<Dept>();
	root = new Dept();
	root.setId(1);
	root.setParentId(0);
	dataBaseList.add(root);
	
	Dept d1_1 = new Dept();
	d1_1.setId(2);
	d1_1.setParentId(1);
	Dept d1_2 = new Dept();
	d1_2.setId(3);
	d1_2.setParentId(1);
	dataBaseList.add(d1_1);
	dataBaseList.add(d1_2);
	
	Dept d1_1_1 = new Dept();
	d1_1_1.setId(4);
	d1_1_1.setParentId(2);
	Dept d1_1_2 = new Dept();
	d1_1_2.setId(5);
	d1_1_2.setParentId(2);
	dataBaseList.add(d1_1_1);
	dataBaseList.add(d1_1_2);
	d1_1.getChildren().add(d1_1_1);
	d1_1.getChildren().add(d1_1_2);
	
	root.getChildren().add(d1_1);
	root.getChildren().add(d1_2);
	System.out.println(root);
	
	Dept newRoot = new Dept();
	newRoot.setId(1);
	newRoot.setParentId(0);
	getChildren(1,newRoot);
	System.out.println(newRoot);
}

/*
 * 树形菜单结构：
 * --1
 *    --2
 *    	 --4
 *       --5
 *    --3
 *    
 * Dept [id=1, parentId=0, 
 * children=[Dept [id=2, parentId=1, 
 *           		children=[Dept [id=4, parentId=2, children=[]], 
 *                            Dept [id=5, parentId=2, children=[]]]], 
 *           Dept [id=3, parentId=1, children=[]]]]
 */
private static List<Dept> getChildren(int id,Dept dept) {
	// 模拟数据库查询parentId为id的下面的子节点
	List<Dept> deptList = getData(id);
	if(deptList != null){
		// 节点下面的子节点
		dept.setChildren(deptList);
		for(Dept deptItem : deptList){
			// 递归调用
			getChildren(deptItem.getId(), deptItem);
		}
	}
	return deptList;
	
}

private static List<Dept> getData(int id) {
	List<Dept> list = new ArrayList<Dept>();
	for(Dept dept : dataBaseList){
		if(dept.getParentId().equals(id)){
			list.add(dept);
		}
	}
	return list;
}

}