TreeTest

package cn.visight.tree;
import cn.hutool.json.JSONUtil;
import cn.visight.modules.sys.entity.SysMenuEntity;
import org.junit.Test;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;
public class TreeTest {
    @Test
    public void testStreamTree() {
        List<SysMenuEntity> list = new ArrayList<>();
        SysMenuEntity s01 = getEntity(1L,0L,"0-1");
        SysMenuEntity s12 = getEntity(2L,1L,"1-2");
        SysMenuEntity s13 = getEntity(3L,1L,"1-3");
        SysMenuEntity s14 = getEntity(4L,1L,"1-4");
        SysMenuEntity s25 = getEntity(5L,2L,"2-5");
        SysMenuEntity s36 = getEntity(6L,3L,"3-6");
        SysMenuEntity s37 = getEntity(7L,3L,"3-7");
        SysMenuEntity s38 = getEntity(8L,3L,"3-8");
        SysMenuEntity s89 = getEntity(9L,8L,"8-9");
        SysMenuEntity s810 = getEntity(10L,8L,"8-10");
        list.add(s01);
        list.add(s12);
        list.add(s13);
        list.add(s14);
        list.add(s25);
        list.add(s36);
        list.add(s37);
        list.add(s38);
        list.add(s89);
        list.add(s810);
        List<TreeMenu> treeMenuList = new ArrayList<>();
        //转换数据,这个是前端需要的格式。
        list.forEach(t->{
            TreeMenu treeMenuNode = new TreeMenu();
            treeMenuNode.setId(t.getId());
            treeMenuNode.setParentId(t.getPid());
            treeMenuNode.setName(t.getName());
            treeMenuList.add(treeMenuNode);
        });
        Map<Long, List<TreeMenu>> groupMap = treeMenuList.stream().collect(Collectors.groupingBy(TreeMenu::getParentId));
        treeMenuList.forEach(treeMenu -> treeMenu.setChildren(groupMap.get(treeMenu.getId())));
        List<TreeMenu> collect = treeMenuList.stream()
                .filter(treeMenu -> treeMenu.getParentId().equals(0L)).collect(Collectors.toList());
        System.out.println(JSONUtil.toJsonStr(collect));
    }
    public static SysMenuEntity getEntity(Long id, Long pid,String name) {
        SysMenuEntity s1 = new SysMenuEntity();
        s1.setId(id);
        s1.setPid(pid);
        s1.setName(name);
        return s1;
    }
}

TreeMenu

package cn.visight.tree;
import java.util.List;
public class TreeMenu {
    private Long id;
    private Long parentId;
    private String name;
    private List<TreeMenu> children;
    public Long getId() {
        return id;
    }
    public void setId(Long id) {
        this.id = id;
    }
    public Long getParentId() {
        return parentId;
    }
    public void setParentId(Long parentId) {
        this.parentId = parentId;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public List<TreeMenu> getChildren() {
        return children;
    }
    public void setChildren(List<TreeMenu> children) {
        this.children = children;
    }
}