Hi

I have created a VF page for which i am tracking the record on particular date.Now i am selecting the date and click on display button then it is displaying all record related to particularr date.if i am clicking display button without selecting any date then it will be diplay a error message 

"Plz select the Date"..How its Possible...
 

<apex:page docType="html-5.0" standardController="MasterCopy__c"  extensions="dateInPBTbaleControllernewOk"  showHeader="false" sidebar="false">


<style type="text/css" media="print">
@media print
{
#non-printable { display: none; }
#printable {
display: block;
width: 100%;
height: 100%;
}
}
</style>

<style type = "text/css">
        .colHeadr {text-align:center;}
        .colHeadrRight{
            text-align:right;
        }
        }
    </style>


        <apex:define name="body">
            
            <div style="width:1000px;margin: 0px auto 10px auto;border: 1px solid black;">
    <apex:form id="tableId">
        <apex:pageBlock >
            
                    <b><apex:outputLabel value="Trial Balance Report On: "  style="font-weight: bold;color:red;"/></b>
                     <apex:inputField value="{!account.DateUpdate__c}" style="font-weight: bold;color:red;"/>
                     
                     
                   <!--- Trial Balance Report On: <apex:input type="date" value="{!dat}"/>-->
                 
                 <apex:commandButton value="Display" action="{!displaingTable}" reRender="tableId" style="font-weight: bold;color:red;" oncomplete="window.opener.location.refresh();" />
        <b><apex:commandLink id="printable"  onclick="JavaScript:window.print();" value="Print"/></b> <br/><br/><br/>
                 <apex:actionFunction name="showMessage" action="{!showMessage}" rerender="jserror"/>
                 
                 <apex:outputPanel rendered="{!If(totalRevenue != totalRevenue1,true,false)}">
                 <apex:outputLabel style="font-weight: bold;color:red;font-size:15px;padding-left:49%"> Debit and Credit Balances do not match. </apex:outputLabel>
                 </apex:outputPanel>
                 
                 <apex:pageblockTable value="{!listAccount }" var="record"  >
                <apex:pageMessages id="jserror" ></apex:pageMessages>
                    <apex:column value="{!record.Master_Name__c}" headerValue="Master Code" headerClass="colHeadr" style="font-weight: bold;font-size:12px;height=18px;text-align:center;"/>
                    <apex:column value="{!record.Master_Code__c}" headerValue="Master Name" headerClass="colHeadr" style="text-align:center;"/>
                    
                    <apex:column value="{!record.Debit_Balance__c}" headerValue="Debit(+)" style="color:green;" headerClass="colHeadrRight" dir="RTL">
                     <apex:facet name="footer" >
        
                   <!---- <apex:outputText value=" Rs.{!totalRevenue}<br/> Rs.{!totalRevenuee}<br/>-----------------<br/> Rs.{!totalRevenuee1}" style="font-weight: bold;color:green;font-size:12px;height=18px;" escape="false">
                      
                       
                    </apex:outputText>-->
                    <apex:outputText value="Rs.{0, number, ###,###,###,##0.00}"  style="font-weight: bold;color:green;font-size:12px;height=18px;float:right;"  >
                        <apex:param value="{!totalRevenue}"  />
                    </apex:outputText> 
                </apex:facet>
            </apex:column>
                    <apex:column value="{!record.Credit_Balance__c}" headerValue="Credit(-)" style="color:red;"  headerClass="colHeadrRight" dir="RTL">
                    <apex:facet name="footer" >
                   
                        
                   <apex:outputText value="Rs.{0, number, ###,###,###,##0.00}"  style="font-weight: bold;color:red;font-size:12px;height=18px;float:right;"  >
                        <apex:param value="{!totalRevenue1}"  />
                    </apex:outputText> 
                </apex:facet>
                 
            </apex:column>
            
           
          
                    </apex:pageblockTable>
                            
                    
        </apex:pageBlock>
    </apex:form>
    
      
      </div>
        </apex:define>
</apex:page>

-----------------------------------------------------------------

public with sharing class dateInPBTbaleControllernewOk {
    public MasterCopy__c account{get;set;}
    public List<MasterCopy__c> listAccount {get;set;}
    public Double totalRevenue {get;set;}
    public Double totalRevenue1 {get;set;}
    public Double totalRevenuee {get;set;}
    public Double totalRevenuee1 {get;set;}
   
    public Date dat {get;set;}
    
    public Map<Date,List<MasterCopy__c>> mapOfDateWithEntry;

    public dateInPBTbaleControllernewOk(ApexPages.StandardController controller){
    
        account = new MasterCopy__c();
        totalRevenue = 0;
        totalRevenue1 = 0;
        totalRevenuee = 0;
        totalRevenuee1 = 0;
        
    }
     
   public void setValues(){
        listAccount  = new List<MasterCopy__c>([SELECT id,  Closing_Balance__c,Credit__c,Credit_Formula__c,Debit_Formula__c,Date__c,DateUpdate__c,Debit__c,Debit_Balance__c,Credit_Balance__c,
        Group__c,Master_Code__c,Master_Name__c,New_Debit__c,New_Credit__c
                        FROM MasterCopy__c
                        order by Name ASC ]);
        mapOfDateWithEntry = new Map<Date,List<MasterCopy__c>>();
        List<MasterCopy__c> listOfEntryData;
        for(MasterCopy__c entry : listAccount){
            if(entry.DateUpdate__c != null){
                if(mapOfDateWithEntry.containsKey(entry.DateUpdate__c)){
                    mapOfDateWithEntry.get(entry.DateUpdate__c).add(entry);
                }
                else{
                    listOfEntryData = new List<MasterCopy__c>();
                    listOfEntryData.add(entry);
                    mapOfDateWithEntry.put(entry.DateUpdate__c,listOfEntryData);
                }
            }
        }
        calculateTotalRevenue();
        calculateTotalRevenue1();
        calculateTotalRevenue2();
   }
   public void displaingTable(){
        setValues();
        
        
        
 
        if(account.DateUpdate__c!= null){
            totalRevenue = 0;
            totalRevenue1 = 0;
            totalRevenuee = 0;
            totalRevenuee1 = 0;
            system.debug('Map '+mapOfDateWithEntry);
            Set<Date> allDateSet = mapOfDateWithEntry.keySet();
            if(allDateSet.contains(account.DateUpdate__c)){
                listAccount = mapOfDateWithEntry.get(account.DateUpdate__c);
            }
            else {
                Date compareDate ;
                Integer count = 0;
                for(Date firstKeydate : allDateSet){
                    compareDate = firstKeydate;
                    break;
                }
                system.debug('Before Compare Date'+compareDate);
                for(Date keyDate : allDateSet){
                    if(keydate < account.DateUpdate__c && keydate > compareDate){
                        compareDate = keyDate;
                    }
                    if(account.DateUpdate__c < keyDate){
                        count ++ ;
                    }
                }
                system.debug('After Compare Date'+compareDate);
                Date requiredDate ;
                
                if(allDateSet.size() == count){
                    requiredDate = [Select DateUpdate__c from MasterCopy__c Order by DateUpdate__c Desc LIMIT 1][0].DateUpdate__c;
                }
                else {
                    requiredDate = compareDate;
                }
                listAccount = mapOfDateWithEntry.get(requiredDate);
            }
        }
       calculateTotalRevenue();
        calculateTotalRevenue1();
        calculateTotalRevenue2(); 
    
    }
     public void calculateTotalRevenue() {
     //for(MasterCopy__c acct2 : listAccount) {
           // if(acct2.Closing_Balance__c!= null)
               // totalRevenuee= acct2.Closing_Balance__c;
                //}
        for(MasterCopy__c acct : listAccount) {
            if(acct.Debit_Balance__c!= null)
                totalRevenue+= acct.Debit_Balance__c;
                
                }
totalRevenuee1=totalRevenuee+totalRevenue;
             
       
        
    }
    
    
    
    public void calculateTotalRevenue2() {
        for(MasterCopy__c acct2 : listAccount) {
            if(acct2.Closing_Balance__c!= null)
                totalRevenuee= acct2.Closing_Balance__c;
            
              
        }
        
    }
    public void calculateTotalRevenue1() {
        for(MasterCopy__c acct1 : listAccount) {
            if(acct1.Credit_Balance__c!= null)
                totalRevenue1+= acct1.Credit_Balance__c;
                 
               
        }
        
    }
    
    public void showMessage() {
        system.debug('ddddddddd');
      if(totalRevenuee1!= totalRevenue1) {
         Apexpages.addMessage(new Apexpages.message(ApexPages.Severity.Error,'Sorry...... You have entered DUPLICATE MASTER CODE'));
      }
    }
}