Nech su definovane 
 - rozhranie Spotrebic
 - Radio
 - Lampa
 - Policka na ktorej su spotrebice
 - main

Teraz na jednej policke mozu byt rozne spotrebice. Upravte triedu Policka tak, aby bola genericka, aby na policke mohli byt len spotrebice jedneho druhu. V maine vytvorte dve policky tak, aby na jednu policku bolo mozne ukladat iba radia, na druhu iba lampy.

public interface Spotrebic {
    void zapni();
    void vypni();
    boolean jeZapnuty();
}

public class Radio implements Spotrebic {
    private boolean zapnuty;

    public Radio() {
        this.zapnuty = false;
    }

    @Override
    public void zapni() {
        zapnuty = true;
    }

    @Override
    public void vypni() {
        zapnuty = false;
    }

    @Override
    public boolean jeZapnuty() {
        return zapnuty;
    }
}

public class Lampa implements Spotrebic{
    private boolean zapnuty;

    public Lampa() {
        zapnuty = false;
    }
            
    @Override
    public void zapni() {
        zapnuty = true;
    }

    @Override
    public void vypni() {
        zapnuty = false;
    }

    @Override
    public boolean jeZapnuty() {
        return zapnuty;
    }
}

public class Policka {
    private Spotrebic[] spotrebiceNaPolicke;

    public Policka() {
        spotrebiceNaPolicke = new Spotrebic [100];
    }
    
    public void pridaj(Spotrebic spotrebic) {
        for (int i = 0; i < spotrebiceNaPolicke.length; i++) {
            if( spotrebiceNaPolicke[i] == null ) {
                spotrebiceNaPolicke[i] = spotrebic;
                return;
            }
        }
    }
    
    public int dajPocetZapnutych() {
        int pocet = 0;
        for(Spotrebic spotrebic : spotrebiceNaPolicke) {
            if( spotrebic != null && spotrebic.jeZapnuty()) {
                pocet ++;
            }
        }
        return pocet;
    }
}

    public static void main(String[] args) {
        Policka polickaSRadiami = new Policka();
        Policka polickaSLampami = new Policka();
        
        Radio r1 = new Radio();
        Radio r2 = new Radio();
        Radio r3 = new Radio();
        Radio r4 = new Radio();
        r1.zapni();

        Lampa l1 = new Lampa();
        Lampa l2 = new Lampa();
        Lampa l3 = new Lampa();
        Lampa l4 = new Lampa();
        l1.zapni();
        l2.zapni();
        l3.zapni();
        
        polickaSRadiami.pridaj(r1);
        polickaSRadiami.pridaj(r2);
        polickaSRadiami.pridaj(r3);
        polickaSRadiami.pridaj(r4);
        polickaSRadiami.pridaj(l1); //nesmie ist skompilovat
        
        polickaSLampami.pridaj(l1);
        polickaSLampami.pridaj(l2);
        polickaSLampami.pridaj(l3);
        polickaSLampami.pridaj(l4);
        polickaSLampami.pridaj(r1); //nesmie ist skompilovat
        
        System.out.println(polickaSRadiami.dajPocetZapnutych()); 
        System.out.println(polickaSLampami.dajPocetZapnutych()); 
    }

--------------------------------------------------------------------------------

Nech je definovana trieda Schranka. 
V triede TypeInfo doplnte deklaraciu metody dajNazovTriedyPrvkuVSchranke tak, aby bola genericka.
Doplnenie vykonajte dvoma sposobmi
a) pouzitim <T>
b) pouzitim <?>
Otestujte metodu spustenim mainu

public class Schranka<T> {
    private T ulozenaInstancia;

    public void uloz(T objekt) {
        ulozenaInstancia = objekt;
    }

    public T daj() {
        return ulozenaInstancia;
    }
}

public class TypeInfo {

    public static String dajNazovTriedyPrvkuVSchranke(Schranka schranka) {
        return schranka.daj().getClass().getName();
    }

    public static void main(String[] args) {
        Schranka<String> text = new Schranka<>();
        Schranka<Number> cislo = new Schranka<>();
        
        text.uloz("abcd");
        cislo.uloz(10);
        
        System.out.println(TypeInfo.dajNazovTriedyPrvkuVSchranke(text));
        System.out.println(TypeInfo.dajNazovTriedyPrvkuVSchranke(cislo));
    }
}

--------------------------------------------------------------------------------

Preco tato tried nie je kompilovatelna?
Ak neviete odpoved pouzite kompilator.

public class Trieda<T> {

    private Trieda() {
    }

    public static Trieda<T> vytvorInstanciu() {
        return new Trieda<>();
    }
}

--------------------------------------------------------------------------------

Nech su definovane triedy
 - GeometrickyUtovar
 - Obdlznik
 - Schranka
Ktore riadky v maine su kompilovatelne?
Na ktorych riadkoch vznikne (moze vzniknut) chyba za behu?

public class GeometrickyUtvar {
}

public class Obdlznik extends GeometrickyUtvar {
}

public class Schranka<T> {
    private T ulozenaInstancia;

    public void uloz(T objekt) {
        ulozenaInstancia = objekt;
    }

    public T daj() {
        return ulozenaInstancia;
    }
}

    public static void main(String[] args) {
        Schranka<Obdlznik> s1 = new Schranka<>();
        Schranka<Obdlznik> s2 = new Schranka<Obdlznik>();
        Schranka<GeometrickyUtvar> s3 = new Schranka<Obdlznik>();
        Schranka<?> s4 = new Schranka<Obdlznik>();
        Schranka<?> s5 = new Schranka<?>();

        s1.uloz(new Obdlznik());
        s2.uloz(new GeometrickyUtvar());
        s3.uloz(new Obdlznik());
        s4.uloz(new Obdlznik());
        s4.uloz("retazec");
        
        Obdlznik obdlznik = (Obdlznik) s4.daj();
        String retazec    = (String) s4.daj();
    }