how to open a alert dialog in android code example

Example: alertdialog show in android

AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setMessage(getResources().getString(R.string.do_you_really_want_to_signout));
        builder.setTitle(getResources().getString(R.string.sign_out));
        builder.setCancelable(false);
        builder.setNegativeButton(getResources().getString(R.string.cancel), new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int which) {
                dialog.cancel();
            }
        });
        builder.setPositiveButton(getResources().getString(R.string.sure), new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int which) {
                Toast.makeText(AccountActivity.this, R.string.log_out_success,
                        Toast.LENGTH_LONG).show();
               
            }
        });

        AlertDialog alert = builder.create();
        alert.show();