Java创建树形结构算法实例代码

java;">import java.io.Serializable;import java.util.ArrayList;import java.util.Collections;import java.util.Comparator;import java.util.Date;import java.util.Iterator;import java.util.List;/** * <Description> 菜单扩展<br> */public class MenuExt implements Serializable {  /**   * 菜单ID   */  private Long id;  /**   * 菜单名称   */  private String name;  /**   * 菜单地址   */  private String url;  /**   * 菜单图标   */  private String icon;  /**   * 父菜单ID   */  private Long parentId;  /**   * 子菜单   */  private List<MenuExt> children = new ArrayList<MenuExt>();  /**   * 菜单顺序   */  private Integer ordby;  /**   * 菜单状态   */  private String state;  //省略Getter和Setter  /**   *    * <Description> 孩子节点排序<br>   *    */  public void sortChildren() {    Collections.sort(children, new Comparator<MenuExt>() {      @Override      public int compare(MenuExt menu1, MenuExt menu2) {        int result = 0;        Integer ordby1 = menu1.getOrdby();        Integer ordby2 = menu2.getOrdby();        Long id1 = menu1.getId();        Long id2 = menu2.getId();        if (null != ordby1 && null != ordby2) {          result = (ordby1 < ordby2 ? -1 : (ordby1 == ordby2 ? 0 : 1));        } else {          result = (id1 < id2 ? -1 : (id1 == id2 ? 0 : 1));        }        return result;      }    });    // 对每个节点的下一层节点进行排序    for (Iterator<MenuExt> it = children.iterator(); it.hasNext();) {      it.next().sortChildren();    }  }  public List<MenuExt> getChildren() {    return children;  }  public void setChildren(List<MenuExt> children) {    this.children = children;  }}

public static List<MenuExt> createTreeMenus(List<MenuExt> menus) {    List<MenuExt> treeMenus = null;    if (null != menus && !menus.isEmpty()) {      // 创建根节点      MenuExt root = new MenuExt();      root.setName("菜单根目录");      // 组装Map数据      Map<Long, MenuExt> dataMap = new HashMap<Long, MenuExt>();      for (MenuExt menu : menus) {        dataMap.put(menu.getId(), menu);      }      // 组装树形结构      Set<Entry<Long, MenuExt>> entrySet = dataMap.entrySet();      for (Entry<Long, MenuExt> entry : entrySet) {        MenuExt menu = entry.getValue();        if (null == menu.getParentId() || 0 == menu.getParentId()) {          root.getChildren().add(menu);        } else {          dataMap.get(menu.getParentId()).getChildren().add(menu);        }      }      // 对树形结构进行二叉树排序      root.sortChildren();      treeMenus = root.getChildren();    }    return treeMenus;  }