1 package com.sun.test;  2   3 import java.util.ArrayList;  4 import java.util.List;  5   6   7 /**  8  * 递归  9  * 10  */ 11 public class Recursion { 12  13     private String id; 14     private String name; 15     private Recursion parent;// 父单元格对象 16     private List
     
       children = new ArrayList
      
       ();// 子单元格集合 17  18     public Recursion() { 19     } 20  21     public Recursion(String id) { 22         this.id = id; 23     } 24      25     /** 26      * 获得所有节点的id 27      * @param r 28      * @param rs 29      */ 30     public static void getIds(Recursion r , List
       
         rs) { 31         if (r.getChildren() != null && r.getChildren().size() > 0) { 32             rs.add(r.getId()); 33             for (Recursion recursion : r.getChildren()) { 34                 getIds(recursion, rs); 35             } 36         } else { 37             rs.add(r.getId()); 38         } 39     } 40      41     public static List
        
          getIds(Recursion r) { 42         List
         
           rs = new ArrayList<>(); 43         if (r.getChildren() != null && r.getChildren().size() > 0) { 44             rs.add(r.getId()); 45             for (Recursion recursion : r.getChildren()) { 46                 rs.addAll(getIds(recursion)); 47             } 48         } else { 49             rs.add(r.getId()); 50         } 51         return rs; 52     } 53      54     /** 55      * 某个对象的子的最大宽度,也就是某个对象他最后一级的孩子节点的个数 56      * @return 57      */ 58     public int getRowNum() { 59         int rowNum = children.size(); 60         for (Recursion hc : children) { 61             if (hc.getRowNum() > 0) { 62                 rowNum += hc.getRowNum() - 1; 63             } 64         } 65         return rowNum; 66     } 67      68     public static void main(String[] args) { 69         Recursion r = new Recursion("r"); 70         Recursion r1 = new Recursion("r1"); 71         Recursion r2 = new Recursion("r2"); 72         Recursion r1_1 = new Recursion("r1_1"); 73         Recursion r1_2 = new Recursion("r1_2"); 74         Recursion r1_3 = new Recursion("r1_3"); 75         Recursion r2_1 = new Recursion("r2_1"); 76         Recursion r2_2 = new Recursion("r2_2"); 77         Recursion r1_1_1 = new Recursion("r1_1_1"); 78         Recursion r1_1_2 = new Recursion("r1_1_2"); 79         Recursion r2_1_1 = new Recursion("r2_1_1"); 80         Recursion r2_1_2 = new Recursion("r2_1_2"); 81         Recursion r2_1_3 = new Recursion("r2_1_3"); 82         r.getChildren().add(r1); 83         r.getChildren().add(r2); 84         r1.getChildren().add(r1_1); 85         r1.getChildren().add(r1_2); 86         r1.getChildren().add(r1_3); 87         r1_1.getChildren().add(r1_1_1); 88         r1_1.getChildren().add(r1_1_2); 89         r2.getChildren().add(r2_1); 90         r2.getChildren().add(r2_2); 91         r2_1.getChildren().add(r2_1_1); 92         r2_1.getChildren().add(r2_1_2); 93         r2_1.getChildren().add(r2_1_3); 94          95         List
          
            rs = new ArrayList<>(); 96 getIds(r, rs); 97 for (String string : rs) { 98 System.out.println(string); 99 }100 System.out.println("--------------------------");101 List
           
             rs1 = getIds(r);102 for (String string : rs1) {103 System.out.println(string);104 }105 System.out.println("--------------------------");106 System.out.println(r.getRowNum());107 }108 109 public String getId() {110 return id;111 }112 113 public void setId(String id) {114 this.id = id;115 }116 117 public String getName() {118 return name;119 }120 121 public void setName(String name) {122 this.name = name;123 }124 125 public Recursion getParent() {126 return parent;127 }128 129 public void setParent(Recursion parent) {130 this.parent = parent;131 }132 133 public List
            
              getChildren() {134 return children;135 }136 137 public void setChildren(List
             
               children) {138 this.children = children;139 }140 141 }
             
            
           
          
         
        
       
      
     

 

测试类结果为

1 r 2 r1 3 r1_1 4 r1_1_1 5 r1_1_2 6 r1_2 7 r1_3 8 r2 9 r2_110 r2_1_111 r2_1_212 r2_1_313 r2_214 --------------------------15 r16 r117 r1_118 r1_1_119 r1_1_220 r1_221 r1_322 r223 r2_124 r2_1_125 r2_1_226 r2_1_327 r2_228 --------------------------29 8

这里我会画出递归的流程，这样递归就显而易见了

 

前面是对实体的应用一般用在拥有主子关系的系统的。还有一种应用可能比较多见，那就是递归json，有个案例可以看一下，就是一个jsonArray字符串，我需要隐藏其中的某些节点，这里json的格式为含有chil

1     /** 2      * var nodes = [ 3      *    {id: "node1", 4      *    children: [ 5      *        {id: "node1_1"}, 6      *        {id: "node1_2"} 7      *    ]} 8      *]; 9      * 递归JSONArray 移除不需要的id,如果子节点都被移除了，那么其父节点也要被移除，以此类推10      * 这里默认过滤最底层节点，如果要过滤所有，只需要稍加改造11      * @param arr json数组12      * @param 拥有的id13      * @return14      */15     @SuppressWarnings("unchecked")16     public static int iterationMenu(JSONArray arr, List
     
       ids) {17         int f = 0;18         for (Iterator
      
        iterator = arr.iterator(); iterator.hasNext();) {19             JSONObject level1Obj = (JSONObject) iterator.next();20             if (level1Obj.containsKey("children")) {21                 int j = iterationMenu(level1Obj.getJSONArray("children"), ids);22                 if (level1Obj.containsKey("id") && ids.contains(level1Obj.getString("id"))) {23                     j++;24                 }25                 if (j == 0) {26                     iterator.remove();27                 } else {28                     f++;29                 }30             } else {31                 if (level1Obj.containsKey("id")) {32                     if (!ids.contains(level1Obj.getString("id"))) {33                         iterator.remove();34                     } else {35                         f++;36                     }37                 }38             }39         }40         return f;41     }
      
     

只要了解了递归的执行顺序，那么上面的代码很容易理解！