Подскажите пожалуйста, кто решил, что требует валидатор

public class Computer {
    public static void main(String[] args) {
        Computer computer = new Computer();
    }
    public Computer(){
        Keyboard keyboard = new Keyboard("New Keyboard");
        Monitor monitor = new Monitor("New Monitor");
        Mouse mouse = new Mouse("New Mouse");
        SystemUnit systemUnit = new SystemUnit("New SystemUnit");
        System.out.println(keyboard.getKeyboardInit());
        System.out.println(monitor.getMonitorInit());
        System.out.println(mouse.getMouseInit());
        System.out.println(systemUnit.getSystemUnitItem());
    }
}
public class Keyboard {
    private final String keyboardInit;

    public Keyboard(String keyboardInit) {
        this.keyboardInit = keyboardInit;
    }

    public String getKeyboardInit() {
        return keyboardInit;
    }
}