--Controller

public with sharing class PagingController
{
    public PageReference deleteselected() {
        return null;
    }

    public string aName;
    public string getaName()
    {
        return aName;
    }
    public void setaName(string b)
    {
        aName=b;
    }
    
   
    public PageReference process()
    {
        system.debug('entered process...');
        for (CategoryWrapper cw : categories)
        {
            system.debug('Selected : ' + cw.checked);
            if(!CategoryWrapper.contains(cw.cat.Id))
            {
                if (cw.checked == true)
                {
                    CategoryWrapper.add(cw.cat.Id);
                    CategoryWrapperList.add(cw.cat);
                   
                    ApexPages.addMessage(new ApexPages.message(ApexPages.severity.INFO,cw.cat.name));
                }
            }
            else if(CategoryWrapper.contains(cw.cat.Id))
            {
                CategoryWrapper.remove(cw.cat.Id);
                system.debug('CategoryWrapper.Size():' +categories.size());
                for(integer i=0;i<categories.size();i++)               
                {
                    if(cw.checked == false && CategoryWrapper.contains(cw.cat.Id))
                    {
                         CategoryWrapperList.remove(i);  
                    }
                }
                //CategoryWrapperList.remove(cw.cat.Id);
            }           
        }
       
                
        System.debug('These are the selected set...' + CategoryWrapper);
        system.debug('These are selected List...' + CategoryWrapperList);
        for(Account a : CategoryWrapperList)
        { 
           system.debug('Ready Accounts..' + CategoryWrapperList);
           system.debug('Ready for updation...'); 
           update a;     
         
        }
       
        return null;
    }

 
    List<categoryWrapper> categories {get;set;}
 
    // instantiate the StandardSetController from a query locator
    public ApexPages.StandardSetController con
    {
        get
        {
            if(con == null)
            {
               
                con = new ApexPages.StandardSetController(Database.getQueryLocator([Select Id, Name,Type FROM Account Order By Name limit 20]));
                //String strQuery = 'select Id, Name, Type from Account where Name like \'%'+aName+'%\'';
                //con = new ApexPages.StandardSetController(Database.Query(strQuery));
                // sets the number of records in each page set
                con.setPageSize(5);
            }
            return con;
        }
        set;
    }
 
    // returns a list of wrapper objects for the sObjects in the current page set
    public List<categoryWrapper> getCategories()
    {
        system.debug('Entereed getcategories...');
        categories = new List<categoryWrapper>();
        for (Account  category : (List<Account>)con.getRecords())
            categories.add(new CategoryWrapper(category));
            //Checking for Previous Page values and checking if the list contains tat id.   
        for(CategoryWrapper cm : categories)
        {
            system.debug('Inside Prevous loop');
            //system.debug('Check if checked:' CategoryWrapper.contains(cm.cat.Id));
            if(CategoryWrapper.contains(cm.cat.Id))
            {   
                system.debug('cm checked:' + cm.checked);
                if(cm.checked == false)
                {
                   cm.checked = true;
                   system.debug('Check the value');
                }
            }
        }
 
        return categories;
    }
 
    // displays the selected items
    Set<Id> CategoryWrapper = new Set<Id>();   
    Map<Id,Account> CategoryWrapperMap = new Map<Id,Account>();
    List<Account> CategoryWrapperList = new List<Account>();

    public PageReference process(String variable)
    {
        if(variable == 'next' || variable =='previous' || variable == 'first' || variable == 'last')
        {
            system.debug('entered next process...');
            for (CategoryWrapper cw : categories)
            {
                system.debug('Selected : ' + cw.checked);
                if (cw.checked == true)
                {
                    if(!CategoryWrapper.contains(cw.cat.Id))
                    {
                        CategoryWrapper.add(cw.cat.Id);
                        //CategoryWrapperMap.put(cw.cat.Id,cw.cat);
                        CategoryWrapperList.add(cw.cat);
                        ApexPages.addMessage(new ApexPages.message(ApexPages.severity.INFO,cw.cat.name));
                    }
                }
                else if(CategoryWrapper.contains(cw.cat.Id))
                {
                    system.debug('CategoryWrapper.Size():' +categories.size());
                    for(integer i=0;i<categories.size();i++)               
                    {
                        if(cw.checked == false && CategoryWrapper.contains(cw.cat.Id))
                        {                           
                             CategoryWrapperList.remove(i);  
                             CategoryWrapper.remove(cw.cat.Id);                           
                        }
                    }
                }                       
            }
            system.debug('Categories added..' +CategoryWrapper);
            //system.debug('CategoriesMap added..' +CategoryWrapperMap);
            system.debug('CategoryList added..' +CategoryWrapperList);
        }       
               
        return null;
    }
 
    // indicates whether there are more records after the current page set.
    public Boolean hasNext
    {
        get
        {
            return con.getHasNext();
        }
        set;
    }
 
    // indicates whether there are more records before the current page set.
    public Boolean hasPrevious
    {
        get
        {
            return con.getHasPrevious();
        }
        set;
    }
 
    // returns the page number of the current page set
    public Integer pageNumber
    {
        get
        {
            return con.getPageNumber();
        }
        set;
    }
 
    // returns the first page of records
    public void first()
    {
        system.debug('Entered first...');
        process('first');

        con.first();
    }
 
    // returns the last page of records
    public void last()
    {
        system.debug('Entered Last...');
        process('last');

        con.last();
    }
 
    // returns the previous page of records
    public void previous()
    {
        system.debug('Entered previous...');
        process('previous');
        con.previous();
    }
 
    // returns the next page of records
    public void next()
    {
        system.debug('Entered Next...');
        //getCategories();
        process('next');
        con.next();
    }
 
    // returns the PageReference of the original page, if known, or the home page.
    public void cancel()
    {
        con.cancel();
    }
   
   
    public class CategoryWrapper
    {
 
        public Boolean checked{ get; set; }
        public Account cat { get; set;}
    
        public CategoryWrapper()
        {
            cat = new Account();
           ;
        }
    
        public CategoryWrapper(Account c)
        {
            cat = c;
           ;
        }    
   }
   
    
}