摘要： 本文主要介绍父子节点的List转 tree

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85

1、构建tree
2、从数据库查询list
3、将list转为tree
 
/**
 * 树节点实体类
 */
@Data
public class TreeNode implements Serializable {

	private static final long serialVersionUID = 7297611707550474985L;
	
	private Integer id;
	
	private Integer parentId;
	
	private String name;
	
	private List<TreeNode> children;
	
	public TreeNode(String id, String name, String parentId) {
		this.id = id;
		this.parentId = parentId;
		this.name = name;
	}
}
	
		
	// 根节点
	private final Integer PARENT_ID=0;

	/**
	 * 方式一：使用for循环实现
	 * @param treeList
	 * @return
	 */
	private List<TreeNode> loopToTree(List<TreeNode> treeList) {
		List<TreeNode> resList = new ArrayList<>();
		
		for (TreeNode parent : treeList) {
			//添加根节点
			if (PARENT_ID==parent.getParentId()) {
				resList.add(parent);
			}
			//添加子节点
			for (TreeNode child : treeList) {
				if (child.getParentId() == parent.getId()) {
					if (parent.getChildren() == null) {
						parent.setChildren(new ArrayList<>());
					}
					parent.getChildren().add(child);
				}
			}
		}
		return resList;
	}


	/**
	 * 方式二：使用递归实现
	 * @param treeList
	 * @return
	 */
	private  List<TreeNode> recursionToTree(List<TreeNode> treeList) {
		List<TreeNode> resList = new ArrayList<>();
		for (TreeNode parent : treeList) {
			if (PARENT_ID==parent.getParentId()) {
				resList.add(findChildren(parent, treeList));
			}
		}
		return resList;
	}
 
	private  TreeNode findChildren(TreeNode parent, List<TreeNode> treeList) {
		for (TreeNode child : treeList) {
			if (parent.getId().equals(child.getParentId())) {
				if (parent.getChildren() == null) {
					parent.setChildren(new ArrayList<>());
				}
				parent.getChildren().add(findChildren(child, treeList));
			}
		}
		return parent;
	}