AlertDialog setButton was deprecated

Java

AlertDialog alert = new AlertDialog.Builder(this).create();
            alert.setTitle("Error");
            alert.setMessage("Sorry, your device doesn't support flash light!");
            alert.setButton(Dialog.BUTTON_POSITIVE,"OK",new DialogInterface.OnClickListener(){

                @Override
                public void onClick(DialogInterface dialog, int which) {
                    finish();
                }
            });

alert.show();

Kotlin

    var alert: AlertDialog = AlertDialog.Builder(this).create()
    alert.setTitle("Error")
    alert.setMessage("Sorry, your device doesn't support flash light!")
    alert.setButton(Dialog.BUTTON_POSITIVE, "OK", DialogInterface.OnClickListener {
            //do your own idea.
            dialog, which -> finish() })
    alert.show()

You can use this but better use a AlertDialog.Builder next time.

   alertDialog.setButton(DialogInterface.BUTTON_POSITIVE,
            "OK", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialogInterface, int i) {

                }
            });

alertDialog=new AlertDialog.Builder(getApplicationContext()).create();
alertDialog.setTitle("Hello");
alertDialog.setMessage("Hai");
alertDialog.setButton(DialogInterface.BUTTON_NEGATIVE, "hai", new DialogInterface.OnClickListener() {
    @Override
    public void onClick(DialogInterface dialog, int which) {
        Toast.makeText(MainActivity.this, "Thanks", Toast.LENGTH_SHORT).show();
    }
});

alertDialog.show();

To make sure your dialogs match the design guidelines, the API now has 3 types of buttons for an AlertDialog: BUTTON_POSITIVE, BUTTON_NEUTRAL and BUTTON_NEGATIVE. This also provides correct positions for right to left support.

I would advice to create your AlertDialog with the builder pattern

AlertDialog.Builder builder = new AlertDialog.Builder(myContext);//Context parameter
builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
    @Override
    public void onClick(DialogInterface dialog, int which) {
            //do stuff
    }
});
builder.setMessage("some message");
AlertDialog alertDialog = builder.create();

More information on the AlertDialog.Builder can be found in the API reference