背景：
数据库中无序的数据要按树形结构出输出，
如图所示：
每一个记录 对应 一条数据库的 数据，
需求来了，那么怎么实现呢，首先最简单的是直接从数据库 按顺序 查出，然后依次打印，
简单点说吧，oracle数据库有相应的语句可以实现，很容易，但是sql server 没有，尝试了下没有成功，
考虑数据库的兼容性，就像把数据到后台去排序，
那么，这也就是这篇雯所说的内容了，排序。至于排序规则就如图所示很明确了。
刚开始说只需要3级结垢，就是每一个节点下面最多只有两个节点，那好，就直接在
compareTo 写 dept.getParnt().getParent() 这样判断，
过了一段时间又说要4级结构….凌乱… 这个方法我又要重写，
现在写一个通用的，，不管多少级都可以
compareTo方法：
@Overridepublic int compareTo(Dept d) {if( this.getRootParent().getId().intValue() != d.getRootParent().getId().intValue() ){//没有相同的parent,那么在不同的根节点之下，按根节点的order排序if(this.getRootParent().getOrder() > d.getRootParent().getOrder()){return 1;}else if(this.getRootParent().getOrder() < d.getRootParent().getOrder()){return -1;}}else{//在同一个根节点下if(isSameBranchAtABranch(d) != null){//在一条线上if( this.getId().intValue() == isSameBranchAtABranch(d).getId().intValue() ){return -1;}else{return 1;}}else{Dept togetherParentFirst = haveSameParentsButBotABranch(d);if(this.getParent().getId().intValue() == togetherParentFirst.getId().intValue()//都是level 2&& d.getParent().getId().intValue() == togetherParentFirst.getId().intValue()){if(this.getOrder().intValue() > d.getOrder().intValue()){return -1;}else if(this.getOrder().intValue() < d.getOrder().intValue()){return 1;}else{return 0;}}Dept temp = this;int orderThis = 0;int orderD = 0;while(temp.getParent() != null){if(temp.getId().intValue() == togetherParentFirst.getId().intValue()){orderThis = temp.getOrder();}else{temp = temp.getParent();}}temp = d;while(temp.getParent() != null){if(temp.getId().intValue() == togetherParentFirst.getId().intValue()){orderD = temp.getOrder();}else{temp = temp.getParent();}}if(orderThis > orderD){return -1;}else if(orderThis < orderD){return 1;}}}return 0;}
完整测试代码：
打印结果如上图所示：
package test;import java.util.ArrayList;import java.util.Collections;import java.util.List;public class Jtest{static ArrayList<Dept> deptList = new ArrayList<Dept>();static{initData();}/** * 主程序入口 * @param args */public static void main(String[] args) {print("===应该的顺序===");iteratorPrintDeptList(deptList);//打印print("===打乱顺序后===");radomSwapList(deptList);iteratorPrintDeptList(deptList);//打印Collections.sort(deptList);//排序print("===排序后===");iteratorPrintDeptListWithLevel(deptList);//打印}//初始化测试数据private static void initData() {Jtest jtest = new Jtest();//这里写为内部类是因为当时想做个其他的测试，忽略Dept deptLevel01_1 = jtest.new Dept(1, "level01_deptLevel01_1", 5, null,null);Dept deptLevel01_2 = jtest.new Dept(2, "level01_deptLevel01_2", 4, null,null);Dept deptLevel01_3 = jtest.new Dept(3, "level01_deptLevel01_3", 3, null,null);Dept deptLevel01_4 = jtest.new Dept(4, "level01_deptLevel01_4", 5, null,null);Dept deptLevel02_1 = jtest.new Dept(5, "level02_deptLevel02_1", 9, 1,deptLevel01_1);Dept deptLevel02_2 = jtest.new Dept(6, "level02_deptLevel02_2", 5, 1,deptLevel01_1);Dept deptLevel02_3 = jtest.new Dept(7, "level02_deptLevel02_3", 6, 1,deptLevel01_1);Dept deptLevel02_4 = jtest.new Dept(8, "level02_deptLevel02_4", 6, 2,deptLevel01_2);Dept deptLevel02_5 = jtest.new Dept(9, "level02_deptLevel02_5", 6, 3,deptLevel01_3);Dept deptLevel02_6 = jtest.new Dept(10, "level02_deptLevel02_6", 8, 3,deptLevel01_3);Dept deptLevel03_1 = jtest.new Dept(11, "level03_deptLevel03_1", 6, 8,deptLevel02_4);Dept deptLevel03_2 = jtest.new Dept(12, "level03_deptLevel03_2", 8, 8,deptLevel02_4);Dept deptLevel03_3 = jtest.new Dept(13, "level03_deptLevel03_3", 6, 5,deptLevel02_1);Dept deptLevel03_4 = jtest.new Dept(14, "level03_deptLevel03_4", 8, 5,deptLevel02_1);deptList.add(deptLevel01_3);deptList.add(deptLevel02_5);deptList.add(deptLevel02_6);deptList.add(deptLevel01_1);deptList.add(deptLevel02_3);deptList.add(deptLevel02_2);deptList.add(deptLevel02_1);deptList.add(deptLevel03_3);deptList.add(deptLevel03_4);deptList.add(deptLevel01_2);deptList.add(deptLevel02_4);deptList.add(deptLevel03_1);deptList.add(deptLevel03_2);deptList.add(deptLevel01_4);}/** * 打乱list的顺序 * @param deptList */static void radomSwapList(List<Dept> deptList){int size = deptList.size();for(int i = 0; i < 30; i++){int randomNum = (int)(Math.random()*10);if(randomNum >= size){continue;}Dept temp = deptList.get(randomNum);deptList.set(randomNum, deptList.get(size – 1 – randomNum));deptList.set(size – 1 – randomNum, temp);}}/** * 遍历打印Arraylist * @param deptList */static void iteratorPrintDeptList(List<Dept> deptList){for(Dept dept : deptList) {System.out.println("deptId: "+""+dept.getId() + ", " + dept.getName() + ", " + dept.getParentId());}print();}/** * 遍历打印Arraylist(按级别缩进) * @param deptList */static void iteratorPrintDeptListWithLevel(List<Dept> deptList){for(Dept dept : deptList) {int level = dept.getLevel();for(int i= 1; i< level; i++){System.out.print("–");}System.out.println("deptId: "+""+dept.getId() + ", " + dept.getName() + ", " + dept.getParentId());}print();}/** * 遍历打印Arraylist * @param deptList */static void simpleIteratorPrintDeptList(List<Dept> deptList){for(Dept dept : deptList) {System.out.print(dept.getId() + ", ");}System.out.println();}static void print(){System.err.println("————————");}static void print(String str){System.err.println(str);}class Dept implements Comparable<Dept>{private Integer id;private String name;private Integer order;private Integer parentId;private Dept parent;/*** 得到当前部门是第几级部门，parent为null的为 1 级，有一个parent的为2级，依次类推*/private int getLevel(){int temp = 1;Dept tempDept = this;while(tempDept.getParent() != null){tempDept = tempDept.getParent();temp = temp +1;}return temp;}private Dept sameParents(Dept d){Dept temp1 = this;while(temp1 != null){Dept temp2 = d;while(temp2 != null){if( temp1.getId() == temp2.getId() ){return temp1;}temp2 = temp2.getParent();}temp1 = temp1.getParent();}return null;}/*** 获得根节点的parent* @return*/private Dept getRootParent(){if(this.getParent() == null){return this;}else{Dept tmp = this;while(tmp.getParent() != null){tmp = tmp.getParent();}return tmp;}}/*** 得到某个level的parent* @param level* @return*/private Dept getParent(int level){int thisLevel = this.getLevel();Dept deptTemp = this;while(deptTemp.getParent() != null){thisLevel = thisLevel – 1;deptTemp = deptTemp.getParent();if(level == thisLevel){return deptTemp;}}return null;}@Overridepublic int compareTo(Dept d) {if( this.getRootParent().getId().intValue() != d.getRootParent().getId().intValue() ){//没有相同的parent,那么在不同的根节点之下，按根节点的order排序if(this.getRootParent().getOrder() > d.getRootParent().getOrder()){return 1;}else if(this.getRootParent().getOrder() < d.getRootParent().getOrder()){return -1;}}else{//在同一个根节点下if(isSameBranchAtABranch(d) != null){//在一条线上if( this.getId().intValue() == isSameBranchAtABranch(d).getId().intValue() ){return -1;}else{return 1;}}else{Dept togetherParentFirst = haveSameParentsButBotABranch(d);if(this.getParent().getId().intValue() == togetherParentFirst.getId().intValue()//都是level 2&& d.getParent().getId().intValue() == togetherParentFirst.getId().intValue()){if(this.getOrder().intValue() > d.getOrder().intValue()){return -1;}else if(this.getOrder().intValue() < d.getOrder().intValue()){return 1;}else{return 0;}}Dept temp = this;int orderThis = 0;int orderD = 0;while(temp.getParent() != null){if(temp.getId().intValue() == togetherParentFirst.getId().intValue()){orderThis = temp.getOrder();}else{temp = temp.getParent();}}temp = d;while(temp.getParent() != null){if(temp.getId().intValue() == togetherParentFirst.getId().intValue()){orderD = temp.getOrder();}else{temp = temp.getParent();}}if(orderThis > orderD){return -1;}else if(orderThis < orderD){return 1;}}}return 0;}/*** 判断是否两个节点有一个共同的父节点(1)(并且两个节点是在一条分支上，就是一个节点是另一个节点的父节点)* @param d 要和当前节点比较的节点* @return 返回父节点（此父节点就是其中的一个节点 ）*/private Dept isSameBranchAtABranch(Dept d){Dept temp = this;while(temp.getParent() != null){if( temp.getParent().getId().intValue() == d.getId() ){return d;}temp = temp.getParent();}temp = d;while(temp.getParent() != null){if( temp.getParent().getId().intValue() == this.getId() ){return this;}temp = temp.getParent();}return null;}/*** 判断是否有相同的父节点(2)（两个节点不位于不同的小分支，此节点不是其中的的任意一个节点,也就是除去1的情况）* @param d* @return*/private Dept haveSameParentsButBotABranch(Dept d){Dept temp = this;while(temp.getParent() != null){if(temp.getParent().isSameBranchAtABranch(d) != null){return temp.getParent();}temp = temp.getParent();}return null;}@Overridepublic String toString() {return this.getId()+", "+this.getParent().getParentId()+", "+this.getName();}/*** 构造函数* @param id* @param name* @param order* @param parentId* @param parent*/public Dept(Integer id, String name, Integer order, Integer parentId,Dept parent) {super();this.id = id;this.name = name;this.order = order;this.parentId = parentId;this.parent = parent;}public Integer getId() {return id;}public void setId(Integer id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public Integer getOrder() {return order;}public void setOrder(Integer order) {this.order = order;}public Dept getParent() {return parent;}public void setParent(Dept parent) {this.parent = parent;}public Integer getParentId() {return parentId;}public void setParentId(Integer parentId) {this.parentId = parentId;}}}
若不给自己设限，则人生中就没有限制你发挥的藩篱。
