Zadanie 1:

/**
 * Created by student on 2019-03-19.
 */
public class klasa1 {
    klasa1(){
        System.out.println(this.getClass().getSimpleName());
    };
    klasa1(String x){
        System.out.println(x + this.getClass().getSimpleName());
    }

    public class klasaZag {
        klasaZag(){
            System.out.println("Klasa zagnieżdżona");
        }
    }
}

/**
 * Created by student on 2019-03-19.
 */
public class main {
    public static void main(String[] args){

        klasa1 k1 = new klasa1();
        klasa1 k2 = new klasa1("Jestem przeladowany ");

        klasa1[] tab1 = new klasa1[10];

        tab1[0] = new klasa1();
        tab1[1] = new klasa1("Jestem przeladowany ");

        klasa1.klasaZag kZ = tab1[0].new klasaZag();
    }
}


Zadanie 2:

import java.util.Random;

public class klasa1 {
    public int ilosc;
    int tablica[];
    klasa1(int ilosc){
        if(ilosc <= 5){
            this.ilosc = ilosc;
            tablica = new int[ilosc];
            Random rand = new Random();
            for(int j = 0; j < tablica.length; j++){
                tablica[j] = rand.nextInt();
                System.out.println("Nr = " + tablica[j]);
            }
        }
        else
            System.out.println("Too big number in parameter..\n");
    }

    void OdwrocTablice(){
        for(int i = 0; i < tablica.length/2; i++){
            int tmp = tablica[i];
            tablica[i] = tablica[tablica.length - i - 1];
            tablica[tablica.length - i - 1] = tmp;
        }
        System.out.println("Odwrona:\n");
        for(int i = 0; i < tablica.length; i++){
            System.out.println("Ns = " + tablica[i]);
        }
    }
    void Rozmiar(){
        int[] vec = new int[2];
        vec[0] = tablica.length;
        vec[1] = tablica.length * Integer.SIZE/8;

        System.out.println("\nLength = " + vec[0] + "\nSize = " + vec[1]);
    }

    void IloscParzystych(){
        int ilParz = 0;
        for(int i = 0; i < tablica.length; i++){
            if(tablica[i] % 2 == 0){
                ilParz++;
            }
        }
        System.out.println("We have " + ilParz + " even numbers.\n");
    }
}


/**
 * Created by student on 2019-03-19.
 */
public class main {
    public static void main(String[] args) {
        klasa1 k1 = new klasa1(5);

        k1.OdwrocTablice();

        k1.Rozmiar();

        k1.IloscParzystych();
    }
}


Zadanie 3:

/**
 * Created by student on 2019-03-19.
 */
public class klasa1 {
    void zjedzPamiec(){
        int tablica[] = new int[500000];
        for(int i = 0, pom = 0; i < 500000; i++){
            tablica[i] = pom;
            pom++;
        }
    }
}


/**
 * Created by student on 2019-03-19.
 */
public class main {
    public static void main(String[] args){
        klasa1 k1 = new klasa1();
        System.out.println(Runtime.getRuntime().freeMemory());
        k1.zjedzPamiec();
        System.out.println(Runtime.getRuntime().freeMemory());
        System.gc();
        System.out.println(Runtime.getRuntime().freeMemory());
    }
}