Why h:dataTable can have hashmap as value

Question

I have a question about the book of core java sever faces. It's in chapter 12 and the title is how do i generate a popup window. page 591.
The book uses <h:dataTable value="#{bb.states[param.country]}" var="state">
But bb.states is a hashmap in backing bean bb. How can it be used as array.
Actually value attribute of <h:dataTable> has to be one of 4 types (array, list, Result, ResultSet).
param.country is the url parameter, it could be USA or Canada.
The book says, "the sates property of the backing bean bb yields a map whose index is the country name"
But hashmap doesn't have index. Could you please help?
Thanks,
Jie
the BackingBean.java is listed below:
package com.corejsf;
import java.util.HashMap;
import java.util.Map;
public class BackingBean {
private String country = "USA";
private String state = "";
private static Map states;
// PROPERTY: country
public String getCountry() { return country; }
public void setCountry(String newValue) { country = newValue; }
// PROPERTY: state
public String getState() { return state; }
public void setState(String newValue) { state = newValue; }
public Map getStates() { return states; }
public String[] getStatesForCountry() { return (String[]) states.get(country); }
static {
states = new HashMap();
states.put("USA",
new String[] {
"Alabama", "Alaska", "Arizona", "Arkansas", "California",
"Colorado", "Connecticut", "Delaware", "Florida", "Georgia",
"Hawaii", "Idaho", "Illinois", "Indiana", "Iowa", "Kansas",
"Kentucky", "Louisiana", "Maine", "Maryland", "Massachusetts",
"Michigan", "Minnesota", "Mississippi", "Missouri", "Montana",
"Nebraska", "Nevada", "New Hampshire", "New Jersey", "New Mexico",
"New York", "North Carolina", "North Dakota", "Ohio", "Oklahoma",
"Oregon", "Pennsylvania", "Rhode Island", "South Carolina",
"South Dakota", "Tennessee", "Texas", "Utah", "Vermont",
"Virginia", "Washington", "West Virginia", "Wisconsin", "Wyoming"
states.put("Canada",
new String[] {
"Alberta", "British Columbia", "Manitoba", "New Brunswick",
"Newfoundland and Labrador", "Northwest Territories",
"Nova Scotia", "Nunavut", "Ontario", "Prince Edward Island",
"Quebec", "Saskatchewan", "Yukon"

Answer 1

The book uses <h:dataTable
value="#{bb.states[param.country]}" var="state">
But bb.states is a hashmap in backing bean bb. How can
it be used as array.
Actually value attribute of <h:dataTable> has to be
one of 4 types (array, list, Result, ResultSet).The value of that expression is the String[] of states.
Notice in your code, you are populating the states Hashmap with String keys and String[] values. The above expression translates to java as:
// grab bb's states property which is a map
Map statesMap = bb.getStates();
// our actual value from the expression is 'states'
String[] states = (String[]) statesMap.get("USA");The DataTable will iterate over the String[] of 'states', which again, is the value of the expression #{bb.states[param.country]} and one of the 4 types you mentioned above.