[android] How to dismiss AlertDialog in android

Here is How I close my alertDialog

lv_three.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
            @Override
            public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {
                GetTalebeDataUser clickedObj = (GetTalebeDataUser) parent.getItemAtPosition(position);
                alertDialog.setTitle(clickedObj.getAd());
                alertDialog.setMessage("Ögrenci Bilgileri Güncelle?");
                alertDialog.setIcon(R.drawable.ic_info);
                // Setting Positive "Yes" Button
                alertDialog.setPositiveButton("Tamam", new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int which) {
                        // User pressed YES button. Write Logic Here
                    }
                });
                alertDialog.setNegativeButton("Iptal", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialogInterface, int i) {
                        //alertDialog.
                        alertDialog.setCancelable(true); // HERE

                    }
                });
                alertDialog.show();
                return true;
            }
        });