java中的日历顺序

Question

公共类 FileDAO 扩展 DaoBase 实现 ITreeDao {File rootDirectory = null;public FileDAO(File rootDirectory) {    if(!rootDirectory.exists()){        throw new IllegalArgumentException("Directory " + rootDirectory.getAbsolutePath() + " doesn't exist");    }    this.rootDirectory = rootDirectory;}protected ITreeNode readRoot(ITree tree) {    tree.setRoot(readNode(this.rootDirectory));    TreeSorter.sortById(tree.getRoot());    return tree.getRoot();}protected Set readChildren(ITreeNode parentNode) {    Set children = new HashSet();    File parentDir = (File) parentNode.getObject();    String[] files = parentDir.list();    if(files == null) return children;    for(int i=0; i<files.length; i++){        File childFile = new File(parentDir.getAbsolutePath() + File.separator + files[i]);        ITreeNode child = readNode(childFile);        child.setParentId(parentNode.getId());        if(!childFile.exists()) continue;        children.add(child);    }    // Sort here    TreeSorter.sortById(parentNode);    return children;}protected Set readGrandChildren(ITreeNode parentNode) {    Set grandChildren = new HashSet();    Iterator children = parentNode.getChildren().iterator();    while(children.hasNext()){        ITreeNode child = (ITreeNode) children.next();        grandChildren.addAll(readChildren(child));    }    return grandChildren;}protected ITreeNode readNode(File file){    if(!file.exists()) return null;    ITreeNode node = null;    String childType = file.isDirectory() ? "directory" : "file";    if(childType.equals("file")){        node = new TreeNode(file.getAbsolutePath(), "<a href=\"openPdf.jsp?fileName=" + file.getAbsolutePath() + "\" target=_blank>" + file.getName() + "</a>" , childType);    }else{        node = new TreeNode(file.getAbsolutePath(), file.getName() , childType);    }    node.setObject(file);    return node;}}在这段代码中，我在readGrandChildren()方法上面临一个问题。就像那里我得到日历月份的升序，但我想显示日历顺序，如 Jan、Feb、Mar.....Dec。请任何人都可以帮助我吗？

Answer 1

使用 TreeSet，通过实现 Comparator 接口并提供反向排序逻辑，最后使用 Collection 接口的 addAll() 方法将 HashSet 的所有元素添加到 TreeSet。

// using Comparator constructor argument of TreeSet

TreeSet < String > ts = new TreeSet < String > (new Comparator < String > () {

 @Override

 public int compare(String o1, String o2) {

  // reverse sorting logic

  return o2.compareTo(o1);

 }

});

// add HashSet elements to TreeSet

ts.addAll(grandChildren);

System.out.println("\n\n\nAfter Sorting : Descending order\n");

// Iterating using Iterator

Iterator < String > ascSorting = ts.iterator();

while (ascSorting.hasNext()) {

 System.out.println(ascSorting.next());

}