当有一个List列表是无序的,List中的数据有parentid进行关联,通过java排序成两种排序类型:
所用的测试列表最顶级无parentid,若为特殊值,修改下判断方法即可。
第一种排序:按照树结构进行排序
排序前:122,13,121,1,131,12,132...
无序的
[TestSort [id=122, name=三级b, parentid=12], TestSort [id=13, name=二级b, parentid=1], TestSort [id=121, name=三级a, parentid=12], TestSort [id=1, name=一级, parentid=null], TestSort [id=131, name=三级c, parentid=13], TestSort [id=12, name=二级a, parentid=1], TestSort [id=132, name=三级d, parentid=13]]
排序后:1,13,131,132,12,122,121...
按照树结构排序
[TestSort [id=1, name=一级, parentid=null], TestSort [id=13, name=二级b, parentid=1], TestSort [id=131, name=三级c, parentid=13], TestSort [id=132, name=三级d, parentid=13], TestSort [id=12, name=二级a, parentid=1], TestSort [id=122, name=三级b, parentid=12], TestSort [id=121, name=三级a, parentid=12]]
测试实体类:
/** * <p>部门列表排序测试类<p> * @version 1.0 * @author li_hao * @date 2018年4月12日 */ public class Dept { private String id; //id private String name; //名称 private String parentid; //父级id public Dept(){ super(); } public Dept(String id, String name, String parentid) { super(); this.id = id; this.name = name; this.parentid = parentid; } public String getId() { return id; } public void setId(String id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getParentid() { return parentid; } public void setParentid(String parentid) { this.parentid = parentid; } @Override public String toString() { return "TestSort [id=" + id + ", name=" + name + ", parentid=" + parentid + "]"; } }
排序代码(第一种排序):
1. 传统方式:
import java.util.ArrayList; import java.util.List; import java.util.Objects; import org.apache.commons.lang.StringUtils; /** * <p>列表排序,按照树结构排序list(顶级无父节点)<p> * 排序前:122,13,121,1,131,12,132... * 无序的 * [TestSort [id=122, name=三级b, parentid=12], TestSort [id=13, name=二级b, parentid=1], TestSort [id=121, name=三级a, parentid=12], TestSort [id=1, name=一级, parentid=null], TestSort [id=131, name=三级c, parentid=13], TestSort [id=12, name=二级a, parentid=1], TestSort [id=132, name=三级d, parentid=13]] * * 排序后:1,13,131,132,12,122,121... * 按照树结构排序 * [TestSort [id=1, name=一级, parentid=null], TestSort [id=13, name=二级b, parentid=1], TestSort [id=131, name=三级c, parentid=13], TestSort [id=132, name=三级d, parentid=13], TestSort [id=12, name=二级a, parentid=1], TestSort [id=122, name=三级b, parentid=12], TestSort [id=121, name=三级a, parentid=12]] * @version 1.0 * @author li_hao * @date 2018年4月12日 */ public class DeptSort { private List<Dept> resultList = new ArrayList<>(); //输出列表 private List<Dept> deptList; //输入列表 /** * 排序 * @param deptList */ public DeptSort(List<Dept> deptList){ this.deptList = deptList; for(Dept dept : this.deptList){ if(StringUtils.isBlank(dept.getParentid())){ //当父级为空 resultList.add(dept); //当父级为空时即顶级,首先放入输出列表 findChildren(dept); //查询下级 } } } /** * 查询下级 * @param dept */ private void findChildren(Dept dept){ List<Dept> childrenList = new ArrayList<>(); //遍历输入列表,查询下级 for(Dept d : deptList){ if(Objects.equals(dept.getId(), d.getParentid())) childrenList.add(d); } //遍历到最末端,无下级,退出遍历 if(childrenList.isEmpty()){ return; } //对下级进行遍历 for(Dept d : childrenList){ resultList.add(d); findChildren(d); } } public List<Dept> getResultList(){ return resultList; } public static List<Dept> sort(List<Dept> originalList){ return new DeptSort(originalList).getResultList(); } /** * 测试 * @param args */ public static void main(String[] args) { List<Dept> originalList = new ArrayList<Dept>(); originalList.add(new Dept("122", "三级b", "12")); originalList.add(new Dept("13", "二级b", "1")); originalList.add(new Dept("121", "三级a", "12")); originalList.add(new Dept("1", "一级", null)); originalList.add(new Dept("131", "三级c", "13")); originalList.add(new Dept("12", "二级a", "1")); originalList.add(new Dept("132", "三级d", "13")); List<Dept> resultList = DeptSort.sort(originalList); System.out.println("输入列表:"+ originalList); System.out.println("输出列表:"+ resultList); } }
2. java8 Stream优化递归:
import java.util.ArrayList; import java.util.List; import java.util.Objects; import java.util.stream.Collectors; import java.util.stream.Stream; import org.apache.commons.lang.StringUtils; /** * java8 Stream 优化递归 * <p>列表排序,按照树结构排序list(顶级无父节点)<p> * 排序前:122,13,121,1,131,12,132... * 无序的 * [TestSort [id=122, name=三级b, parentid=12], TestSort [id=13, name=二级b, parentid=1], TestSort [id=121, name=三级a, parentid=12], TestSort [id=1, name=一级, parentid=null], TestSort [id=131, name=三级c, parentid=13], TestSort [id=12, name=二级a, parentid=1], TestSort [id=132, name=三级d, parentid=13]] * * 排序后:1,13,131,132,12,122,121... * 按照树结构排序 * [TestSort [id=1, name=一级, parentid=null], TestSort [id=13, name=二级b, parentid=1], TestSort [id=131, name=三级c, parentid=13], TestSort [id=132, name=三级d, parentid=13], TestSort [id=12, name=二级a, parentid=1], TestSort [id=122, name=三级b, parentid=12], TestSort [id=121, name=三级a, parentid=12]] * @version 1.0 * @author li_hao * @date 2018年4月12日 */ public class DeptSortJava8 { private List<Dept> deptList; public DeptSortJava8(List<Dept> deptList) { this.deptList = deptList; } public static List<Dept> sort(List<Dept> originalList) { return new DeptSortJava8(originalList).sort(); } private List<Dept> sort() { return this.deptList.stream() .filter(d -> StringUtils.isBlank(d.getParentid())) .flatMap(d -> Stream.concat(Stream.of(d), findChildren(d))) .collect(Collectors.toList()); } /** * 查询下级部门 * @param dept */ private Stream<Dept> findChildren(Dept dept) { return deptList.stream() .filter(d -> Objects.equals(dept.getId(), d.getParentid())) .flatMap(d -> Stream.concat(Stream.of(d), findChildren(d))); } /** * 测试 * @param args */ public static void main(String[] args) { List<Dept> originalList = new ArrayList<Dept>(); originalList.add(new Dept("122", "三级b", "12")); originalList.add(new Dept("13", "二级b", "1")); originalList.add(new Dept("121", "三级a", "12")); originalList.add(new Dept("1", "一级", null)); originalList.add(new Dept("131", "三级c", "13")); originalList.add(new Dept("12", "二级a", "1")); originalList.add(new Dept("132", "三级d", "13")); List<Dept> resultList = DeptSortJava8.sort(originalList); System.out.println("输入列表:"+ originalList); System.out.println("输出列表:"+ resultList); } }
测试结果:
排序前:
[TestSort [id=122, name=三级b, parentid=12], TestSort [id=13, name=二级b, parentid=1], TestSort [id=121, name=三级a, parentid=12], TestSort [id=1, name=一级, parentid=null], TestSort [id=131, name=三级c, parentid=13], TestSort [id=12, name=二级a, parentid=1], TestSort [id=132, name=三级d, parentid=13]]
排序后:
[TestSort [id=1, name=一级, parentid=null], TestSort [id=13, name=二级b, parentid=1], TestSort [id=131, name=三级c, parentid=13], TestSort [id=132, name=三级d, parentid=13], TestSort [id=12, name=二级a, parentid=1], TestSort [id=122, name=三级b, parentid=12], TestSort [id=121, name=三级a, parentid=12]]
第二种排序:按照层级从上到下进行排序,同级的放一块
排序前:122,13,121,1,131,12,132...
无序的
[TestSort [id=122, name=三级b, parentid=12], TestSort [id=13, name=二级b, parentid=1], TestSort [id=121, name=三级a, parentid=12], TestSort [id=1, name=一级, parentid=null], TestSort [id=131, name=三级c, parentid=13], TestSort [id=12, name=二级a, parentid=1], TestSort [id=132, name=三级d, parentid=13]]
排序后:1,13,12,131,132,122,121...
按照层级排序
[TestSort [id=1, name=一级, parentid=null], TestSort [id=13, name=二级b, parentid=1], TestSort [id=12, name=二级a, parentid=1], TestSort [id=131, name=三级c, parentid=13], TestSort [id=132, name=三级d, parentid=13], TestSort [id=122, name=三级b, parentid=12], TestSort [id=121, name=三级a, parentid=12]]
排序代码(第二种排序):
1. 传统方式:
import java.util.ArrayList; import java.util.Iterator; import java.util.List; import java.util.Objects; import java.util.TreeMap; import org.apache.commons.lang.StringUtils; /** * * <p>列表排序,按照层级从上到下排序list,同级的放一块(顶级无父节点)<p> * * 排序前:122,13,121,1,131,12,132... * 无序的 * [TestSort [id=122, name=三级b, parentid=12], TestSort [id=13, name=二级b, parentid=1], TestSort [id=121, name=三级a, parentid=12], TestSort [id=1, name=一级, parentid=null], TestSort [id=131, name=三级c, parentid=13], TestSort [id=12, name=二级a, parentid=1], TestSort [id=132, name=三级d, parentid=13]] * * 排序后:1,13,12,131,132,122,121... * 按照层级排序 * [TestSort [id=1, name=一级, parentid=null], TestSort [id=13, name=二级b, parentid=1], TestSort [id=12, name=二级a, parentid=1], TestSort [id=131, name=三级c, parentid=13], TestSort [id=132, name=三级d, parentid=13], TestSort [id=122, name=三级b, parentid=12], TestSort [id=121, name=三级a, parentid=12]] * @version 1.0 * @author li_hao * @date 2018年4月12日 */ public class DeptSort2 { private TreeMap<Integer, List<Dept>> treeMap; //定义一个treeMap,key是等级,value是当前的等级对应的所有对象list private Integer level = 2; private List<Dept> resultList = new ArrayList(); //输出列表 private List<Dept> deptList; //输入列表 /** * 排序 * @param deptList */ public DeptSort2(List<Dept> deptList) { this.deptList = deptList; for (Dept dept : this.deptList) { if (StringUtils.isBlank(dept.getParentid())) { //当父级为空 resultList.add(dept); //当父级为空时即顶级,首先放入输出列表 treeMap = new TreeMap<>(); findChildren(dept); //查询下级 Iterator it = treeMap.keySet().iterator(); //迭代treeMap while (it.hasNext()) { //检查序列中是否还有元素,如果迭代中还有元素返回true(因为treeMap中放的是2级和2级下面的所有list,所以只需要判断it.hashNext) resultList.addAll(treeMap.get(it.next())); //把treeMap中所有的list按照层级顺序添加到resultList中 } } } } /** * 查询下级部门 * 方法进去的时候就记录当前层级数,findchildren方法走完的时候,表示这一层已经没有逻辑了,递归回上一层,所以 this点level减一 * @param dept */ private void findChildren(Dept dept) { Integer level = this.level++; //第一次进来时level值为2,this.level值为3 try { List<Dept> childrenList = new ArrayList<>(); //遍历输入列表,查询下级 for (Dept d : deptList) { if (Objects.equals(dept.getId(), d.getParentid())) childrenList.add(d); } //遍历到最末端,无下级,退出遍历 if (childrenList.isEmpty()) { return; } //对下级进行遍历 for (Dept d : childrenList) { addToMap(level, d); //向treeMap中添加等级和对应dept(第一次执行的level值为2) findChildren(d); //查询下级,(比如:第一次进来时level值为2,this.level值为3,在进入此方法后,level为3,this.level为4,没查到则跳出,level减一) } } finally { this.level--; //由于再次执行findChildren时,this.level的值+1了,那么在执行完毕后需要finally:this.level-- } } /** * 向treeMap中添加等级和对应的List * @param level * @param dept */ void addToMap(Integer level, Dept dept) { if (Objects.isNull(treeMap.get(level))) treeMap.put(level, new ArrayList<Dept>()); //先判断下对应层级在map里有没有,没有就初始化,给个list treeMap.get(level).add(dept); //若treeMap中有等级,则添加dept } public List<Dept> getResultList() { return resultList; } public static List<Dept> sort(List<Dept> originalList) { return new DeptSort2(originalList).getResultList(); } /** * 测试 * @param args */ public static void main(String[] args) { List<Dept> originalList = new ArrayList<Dept>(); originalList.add(new Dept("122", "三级b", "12")); originalList.add(new Dept("13", "二级b", "1")); originalList.add(new Dept("121", "三级a", "12")); originalList.add(new Dept("1", "一级", null)); originalList.add(new Dept("131", "三级c", "13")); originalList.add(new Dept("12", "二级a", "1")); originalList.add(new Dept("132", "三级d", "13")); List<Dept> resultList = DeptSort2.sort(originalList); System.out.println("输入列表:"+ originalList); System.out.println("输出列表:"+ resultList); } }
2. java8 Stream优化递归:
import java.util.ArrayList; import java.util.List; import java.util.Objects; import java.util.stream.Collectors; import org.apache.commons.lang.StringUtils; /** * java8 Stream 优化递归 * <p>列表排序,按照层级从上到下排序list,同级的放一块(顶级无父节点)<p> * * 排序前:122,13,121,1,131,12,132... * 无序的 * [TestSort [id=122, name=三级b, parentid=12], TestSort [id=13, name=二级b, parentid=1], TestSort [id=121, name=三级a, parentid=12], TestSort [id=1, name=一级, parentid=null], TestSort [id=131, name=三级c, parentid=13], TestSort [id=12, name=二级a, parentid=1], TestSort [id=132, name=三级d, parentid=13]] * * 排序后:1,13,12,131,132,122,121... * 按照层级排序 * [TestSort [id=1, name=一级, parentid=null], TestSort [id=13, name=二级b, parentid=1], TestSort [id=12, name=二级a, parentid=1], TestSort [id=131, name=三级c, parentid=13], TestSort [id=132, name=三级d, parentid=13], TestSort [id=122, name=三级b, parentid=12], TestSort [id=121, name=三级a, parentid=12]] * @version 1.0 * @author li_hao * @date 2018年4月12日 */ public class DeptSortJava82 { private List<Dept> deptList; private List<Dept> resultList = new ArrayList<>(); public DeptSortJava82(List<Dept> deptList) { this.deptList = deptList; } public static List<Dept> sort(List<Dept> originalList) { return new DeptSortJava82(originalList).sort(); } private List<Dept> sort() { this.deptList.stream() .filter(d -> StringUtils.isBlank(d.getParentid())) .forEach(d -> { resultList.add(d); findChildren(d); }); return resultList; } /** * 查询下级部门 * * @param dept */ private void findChildren(Dept dept) { List<Dept> childrenList = deptList.stream() .filter(d -> Objects.equals(dept.getId(), d.getParentid())) .collect(Collectors.toList()); if (childrenList.isEmpty()) /* 跳出递归 */ return; else childrenList.forEach(d -> { resultList.add(d); findChildren(d); }); } public static void main(String[] args) { List<Dept> originalList = new ArrayList<Dept>(); originalList.add(new Dept("122", "三级b", "12")); originalList.add(new Dept("13", "二级b", "1")); originalList.add(new Dept("121", "三级a", "12")); originalList.add(new Dept("1", "一级", null)); originalList.add(new Dept("131", "三级c", "13")); originalList.add(new Dept("12", "二级a", "1")); originalList.add(new Dept("132", "三级d", "13")); List<Dept> resultList = DeptSortJava82.sort(originalList); System.out.println("输入列表:"+ originalList); System.out.println("输出列表:"+ resultList); } }
测试结果:
排序前:
[TestSort [id=122, name=三级b, parentid=12], TestSort [id=13, name=二级b, parentid=1], TestSort [id=121, name=三级a, parentid=12], TestSort [id=1, name=一级, parentid=null], TestSort [id=131, name=三级c, parentid=13], TestSort [id=12, name=二级a, parentid=1], TestSort [id=132, name=三级d, parentid=13]]
排序后:
[TestSort [id=1, name=一级, parentid=null], TestSort [id=13, name=二级b, parentid=1], TestSort [id=12, name=二级a, parentid=1], TestSort [id=131, name=三级c, parentid=13], TestSort [id=132, name=三级d, parentid=13], TestSort [id=122, name=三级b, parentid=12], TestSort [id=121, name=三级a, parentid=12]]