i want to create a vf page with account and contact object in a picklist and when we select any object its data should display?

<apex:page controller="AccountContactController">
    <apex:form >
        <apex:pageBlock title="Account Name">
            <apex:selectList value="{!selectedAccId}" size="1">
                <apex:selectOptions value="{!AccountNames}" />
                <apex:actionSupport event="onchange" action="{!showContacts}" reRender="relatedContactsBlock" />
            </apex:selectList><br/><br/>
            <b>Related Contacts</b>
            <apex:pageblockTable title="Contacts" value="{!conlist}" var="sc" id="relatedContactsBlock">
                <apex:column value="{!sc.name}"/>
                <apex:column value="{!sc.phone}"/>
            </apex:pageblockTable>
        </apex:pageBlock>
    </apex:form>
</apex:page>

Public with sharing class AccountContactController {
    Public Id selectedAccId{get;set;} 
    Public List<Contact> Conlist{get;set;}   
    Public List<SelectOption> getAccountNames() {
        List<SelectOption> accOptions= new List<SelectOption>();
        system.debug(selectedAccId);
        accOptions.add( new SelectOption('','--Select--'));
        for(Account acc : [select Id,name from Account ] ) {
            accOptions.add(new SelectOption(acc.Id,acc.name));
        }
        return accOptions;
    }
    public void refreshContactList(){
        Conlist = new List<Contact>();
        Conlist = [select name,phone from Contact where Accountid=: selectedAccId];
    }
}