java - set boolean value to Realm database when checkbox is checked -

i have realm database model want display in arecyclerview, every row in database model have string name,int age , boolean favourite,when try save boolean value in recyclerviewadapter using interface gjava.lang.nullpointerexception: attempt invoke virtual method 'void io.realm.realm.begintransaction()' on null object reference

this model

public class person extends realmobject implements{ @primarykey private string name; private string job; private boolean favourite; private string image;  public authorinfo(string image, string job, string name, boolean favoutite) {     this.image = image;     this.job = job;     this.name = name;     this.favourite = favourite; }  public authorinfo() { }  public string getimage() {     return image; }  public void setimage(string image) {     this.image = image; }  public string getjob() {     return job; }  public void setjob(string job) {     this.job = job; }  public string getname() {     return name; }  public void setname(string name) {     this.name = name; }  public boolean isfavourite() {     return favourite; }  public void setfavourite(boolean favourite) {     this.favourite = favourite; } 

}

this interface

  public interface itemclicklistener { void onitemclick(view view,int position);} 

and recyclerview adapter

public class personadapter extends recyclerview.adapter<authoradapter.myviewholder> { private layoutinflater inflater; private realm mrealm; private realmresults<authorinfo> results;   public personadapter(context context, realmresults<authorinfo> realmresults) {     inflater = layoutinflater.from(context);     results = realmresults; }   @override public myviewholder oncreateviewholder(viewgroup parent, int viewtype) {      view view = inflater.inflate(r.layout.custom_row, parent, false);     myviewholder holder = new myviewholder(view);     return holder; }  @override public void onbindviewholder(myviewholder holder, final int position) {     authorinfo current = results.get(position);      holder.name.settext(current.getname());     holder.job.settext(current.getjob());     holder.setclicklistener(new itemclicklistener() {    mrealm.begintransaction();        @override         public void onitemclick(view view, int position) {             checkbox chk= (checkbox) view;             if (chk.ischecked()){                 results.get(position).setfavourite(true);             }             else if (!chk.ischecked()){                 results.get(position).setfavourite(false);             }          }          mrealm.committransaction();          notifyitemchanged(position)     });   }   @override public int getitemcount() {     return results.size(); }  public static class myviewholder extends recyclerview.viewholder implements view.onclicklistener {     textview name;     textview job;     checkbox checkbox;      itemclicklistener itemclicklistener;      public myviewholder(view itemview) {         super(itemview);          name = (textview) itemview.findviewbyid(r.id.tv_name);         job = (textview) itemview.findviewbyid(r.id.tv_job);         checkbox = (checkbox) itemview.findviewbyid(r.id.checkbox);         checkbox.setonclicklistener(this);      }      public void setclicklistener(itemclicklistener ic) {         this.itemclicklistener = ic;      }       @override     public void onclick(view view) {         this.itemclicklistener.onitemclick(view,getadapterposition());      } } 

}

so , ideas?!