public class wrapperclass 
{
    public list<displaywrapper> oppdata{get;set;}

    public wrapperclass(ApexPages.StandardController controller)
    {
        if(oppdata == null)
        {    
            oppdata = new list<displaywrapper>();          
            for(Opportunity o1 : [select id,name,closedate,type,stagename,amount from Opportunity])
            {
                oppdata.add(new displaywrapper(o1,true));
            }
        }
    }
    public class displaywrapper
    {
        public opportunity oppflag{get;set;}
        public boolean boo{get;set;}
        
        public displaywrapper(opportunity opp,boolean b1)
        {
            //opp=oppflag;
            oppflag=opp;
            //b1=boo;
            boo=b1;
        }
    }
}

<apex:page standardController="opportunity" extensions="wrapperclass">
<apex:form >
    <apex:pageBlock >
        <apex:pageBlockTable value="{!oppdata}" var="v">
            <apex:column value="{!v.oppflag.name}"/>
            <apex:column value="{!v.oppflag.CloseDate}"/>
            <apex:column value="{!v.oppflag.Type}"/>
            <apex:column value="{!v.oppflag.StageName}"/>
            <apex:column value="{!v.oppflag.Amount}"/>
            <apex:column >
            <apex:inputCheckbox value="{!v.oppflag}"/>
            </apex:column>
       </apex:pageBlockTable>
    </apex:pageBlock>
</apex:form>
</apex:page>