HashMap＆amp; Java中的HashSet size（）

Question

我试图找到有关它的信息但失败了。

size()或HashMap中的HashSet如何实施？它是如何工作的？是O(1)还是O(n)操作？

Answer 1

需要size次。 HashMap有一个/** * Returns the number of key-value mappings in this map. * * @return the number of key-value mappings in this map */ public int size() { return size; } 实例变量，在添加或删除条目时会被修改：

这是HashSet实施：

size()

HashMap调用了<%@ Control Language="C#" AutoEventWireup="true" Inherits="CMSWebParts_General_ResetPassword" CodeBehind="~/CMSWebParts/General/ResetPassword.ascx.cs" %> <div id="reset-password-page" class="col-md-12"> <div class="col-md-3"> </div> <div class="col-md-6"> <h1 style="color: white; margin-top: 0px;">Reset Password</h1> <div style="margin-top: 30px; color: #eb770a!important; padding-left: 20px;" class="row"> <div class="form-group row"> <span style="color: red; position: relative; left: 12px;" id="validation"></span> </div> <div class="form-group row"> <asp:Label ID="lblPassword" runat="server" Text="Password:" CssClass="col-sm-3 control-label">Password:</asp:Label> <div class="col-sm-9"> <asp:TextBox ID="txtPassword" runat="server" Text="" TextMode="Password" CssClass="form-control" ClientIDMode="Static" Monitor="Monitor" data-rel="password"></asp:TextBox> </div> </div> <div class="form-group row"> <asp:Label ID="lblPassword2" runat="server" Text="Repeat Password:" CssClass="col-sm-3 control-label">Repeat Password:</asp:Label> <div class="col-sm-9"> <asp:TextBox ID="txtPassword2" runat="server" Text="" TextMode="Password" CssClass="form-control" ClientIDMode="Static" Monitor="Monitor" data-rel="password"></asp:TextBox> </div> </div> <div class="form-group row"> <div class="offset-sm-2 col-sm-10" id="reset"> <asp:Button ID="ResetBtn" runat="server" CssClass="btn caseFileButton" Text="Reset" CausesValidation="True" /> </div> </div> </div> </div> <div class="col-md-3"></div> 的{​​{1}}。