В чем ошибка ( Java)

public class MainActivity extends AppCompatActivity {
    int quantity = 0;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    public void increaseQuantity(View view) {
        quantity = quantity + 1;
        TextView QuantityTextView = findViewById(R.id.koll_vo);
        QuantityTextView.setText("" + quantity);


    }

    public void decideQuantity(View view) {
        quantity = quantity - 1;
            if ( quantity < 0);
                quantity = 0;
        TextView QuantityTextView = findViewById (R.id.koll_vo );
        QuantityTextView.setText("" + quantity) ;
    }
}