public List<MYWrapperClass> listWrapper {get;set;}
public Boolean allBool {get;set;}

public DeletingCheckedRowsController() {
    listWrapper = new List<MYWrapperClass>();
    List<account> listEmp = [SELECT Id, Name from account where name like 'a%' ];
    if(listEmp.size() > 0) {
        for(Account emp : listEmp) {
            listWrapper.add(new MYWrapperClass(emp));
        }
    }
}


public void del() {
    List<Account> listEmpForDel = new List<Account>();
    List<MYWrapperClass> listTempWrapper = new List<MYWrapperClass>();
    for(MYWrapperClass w : listWrapper) {
        if(w.checked) {
            listEmpForDel.add(w.emp);
        } else {
            listTempWrapper.add(w);
        }
    }
    if(listEmpForDel.size() > 0) {
        delete listEmpForDel;
        listWrapper = listTempWrapper;
    } else {
        ApexPages.addMessage(new ApexPages.Message(ApexPages.Severity.Error,'Select atleast one record to delete'));
    }
    //return null;
}

public void selectAll() {
    if(allBool) {
        for(MYWrapperClass w : listWrapper) {
            w.checked = true;
        }
    } else {
        for(MYWrapperClass w : listWrapper) {
            w.checked = false;
        }
    }
}



 public class MYWrapperClass {
    public Boolean checked {get;set;}
    public account emp {get;set;}
    public MYWrapperClass(account aemp) {
        this.emp = aemp;
    }
}