Java排序列表 [英] Java sorting List

问题描述

我在java中有一个List。我从SQL查询中获取值。

I got a List in java. I get values from a SQL query.

public void ReloadPages() throws Exception {        
    try (Connection conn = Framework.GetDatabaseManager().GetBone().getConnection()) {
        try (ResultSet set = conn.createStatement().executeQuery("SELECT * FROM habbo_shop_pages")) {
            while (set.next()) {
                int Id = set.getInt(1);

                Pages.put(Id, new CatalogPage(set));
            }
        }
    }

    System.out.println("Loaded " + Pages.size() + " Catalog Page(s).");
}

然后我将它全部存储起来。在另一个函数中，我想从parentid中检索某些页面。

Then I store it all. In another function, I want to retrieve certain pages from a parentid.

public LinkedList<CatalogPage> getSubPages(int parentId) {
    LinkedList<CatalogPage> pages = new LinkedList<>();

    for (CatalogPage page : this.Pages.values()) {
        if (page.getParentId() != parentId) {
            continue;
        }

        pages.add(page);
    }

    return pages;
}

如何订购清单？现在id 4位于商店上方，1位于底部，但我想按ID排序。查询中的ORDER BY不起作用。

How do I order the list? Now id 4 is above in the shop and 1 at the bottom, but I want it ordered by id. ORDER BY in query doesn't work.

推荐答案

让你的类实现 可比较 并在< a href =http://docs.oracle.com/javase/7/docs/api/java/lang/Comparable.html#compareTo%28T%29 =noreferrer> compareTo 方法。要排序，只需使用 集合#sort ，但请注意它是内联排序。

Have your class implement Comparable and provide said sort ordering in compareTo method. And to sort, simply use Collections#sort, although be aware that it's an inline sort.

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