在Java中创建购物车。对使用Hashmap感到困惑_Java_Html_Jsf

在Java中创建购物车。对使用Hashmap感到困惑

java html jsf

在Java中创建购物车。对使用Hashmap感到困惑,java,html,jsf,Java,Html,Jsf,选择豆包sessiontracking import java.io.Serializable; import java.util.HashMap; import java.util.Set; import java.util.TreeSet; import javax.faces.bean.ManagedBean; import javax.faces.bean.SessionScoped; @ManagedBean( name="selectionsBean" ) @SessionSco

选择豆包sessiontracking

import java.io.Serializable;
import java.util.HashMap;
import java.util.Set;
import java.util.TreeSet;
import javax.faces.bean.ManagedBean;
import javax.faces.bean.SessionScoped;

@ManagedBean( name="selectionsBean" )
@SessionScoped
public class SelectionsBean implements Serializable
{
   // map of topics to book titles
   private static final HashMap< String, Double > booksMap =
      new HashMap< String, Double >();
   double total;
   // initialize booksMap
   static 
   {
      booksMap.put( "java", 19.99 );
      booksMap.put( "cpp", 29.99 );
      booksMap.put( "iphone",
         32.99 );
      booksMap.put( "android",
         15.99 );
   } // end static initializer block

   // stores individual user's selections
   private Set< String > selections = new TreeSet< String >();
   private String selection; // stores the current selection

   // return number of selections
   public int getNumberOfSelections()
   {
      return selections.size();
   } // end method getNumberOfSelections

   // returns the current selection
   public String getSelection()
   {
      return selection;
   } // end method getSelection

   // store user's selection
   public void setSelection( String topic )
   {
      selection = booksMap.get( topic );
      selections.add( selection );
   } // end method setSelection

   // return the Set of selections
   public String[] getSelections()
   {
      return selections.toArray( new String[ selections.size() ] );
   } // end method getSelections
} // end class SelectionsBean

index.html：

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
   "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
   xmlns:h="http://java.sun.com/jsf/html"
   xmlns:f="http://java.sun.com/jsf/core">
   <h:head>
      <title>Topic Selection Page</title>
   </h:head>
   <h:body>
      <h1>Welcome to Sessions!</h1>
      <p>You have made #{selectionsBean.numberOfSelections} selection(s)
      </p>
      <h3>Make a Selection and Press Submit</h3>
      <h:form>
         <h:selectOneRadio id="topicSelectOneRadio" required="true"
            requiredMessage="Please choose a book, then press Submit"
            value="#{selectionsBean.selection}">
            <f:selectItem itemValue="java" itemLabel="Java How to Program"/>
            <f:selectItem itemValue="cpp" itemLabel="How to C++"/>
            <f:selectItem itemValue="iphone" itemLabel="Learn All About iPhone"/>
            <f:selectItem itemValue="android" itemLabel="Everything to learn Apps"/>
         </h:selectOneRadio>
         <p><h:commandButton value="Submit"/></p>
      </h:form>
      <p><h:outputLink value="recommendations.xhtml">
         Click here for book recommendations
      </h:outputLink></p>
   </h:body>
</html>

建议.xhtml

<html xmlns="http://www.w3.org/1999/xhtml"
   xmlns:h="http://java.sun.com/jsf/html"
   xmlns:ui="http://java.sun.com/jsf/facelets">
   <h:head>
      <title>Recommended Books</title>
   </h:head>
   <h:body>
      <h1>Book Recommendations</h1>
      <ul>
         <ui:repeat value="#{selectionsBean.selections}" var="book">
            <li>#{book}</li>
         </ui:repeat>
      </ul>
      <p><h:outputLink value="index.xhtml">
            Click here to choose another topic
         </h:outputLink></p>
   </h:body>
</html>

我试图做的是，当我运行index.html时，它将显示四本java书籍，用户可以像购物车一样选择和提交这些书籍，并在您结账时显示购物车和总价。我的问题是，使用hashmap，我试图将它的第二个值更改为double，但没有效果。我是否错误地使用了hashmap？

将其第二个值更改为double，但没有效果。这是什么意思；博士，这是太多的代码了。把范围缩小到SSCCE，问题是什么？发生了什么你没有预料到的事？