NP lab 1 Niza od celi broevi

//package naprednolabs;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Arrays;
import java.util.Random;
import java.util.Scanner;
import static java.util.Arrays.*;
public class IntegerArrayTester {
    public static void main(String[] args) throws IOException {
        Scanner scanner = new Scanner(System.in);
        String s = scanner.nextLine();
        IntegerArray ia = null;
        switch (s) {
            case "testSimpleMethods":
                ia = new IntegerArray(generateRandomArray(scanner.nextInt()));
                testSimpleMethods(ia);
                break;
            case "testConcat":
                testConcat(scanner);
                break;
            case "testEquals":
                testEquals(scanner);
                break;
            case "testSorting":
                testSorting(scanner);
                break;
            case "testReading":
                testReading(new ByteArrayInputStream(scanner.nextLine().getBytes()));
                break;
            case "testImmutability":
                int a[] = generateRandomArray(scanner.nextInt());
                ia = new IntegerArray(a);
                testSimpleMethods(ia);
                testSimpleMethods(ia);
                IntegerArray sorted_ia = ia.getSorted();
                testSimpleMethods(ia);
                testSimpleMethods(sorted_ia);
                sorted_ia.getSorted();
                testSimpleMethods(sorted_ia);
                testSimpleMethods(ia);
                a[0] += 2;
                testSimpleMethods(ia);
                ia = ArrayReader.readIntegerArray(new ByteArrayInputStream(integerArrayToString(ia).getBytes()));
                testSimpleMethods(ia);
                break;
        }
        scanner.close();
    }

    static void testReading(InputStream in) throws IOException {
        IntegerArray read = ArrayReader.readIntegerArray(in);
        System.out.println(read);
    }

    static void testSorting(Scanner scanner) {
        int[] a = readArray(scanner);
        IntegerArray ia = new IntegerArray(a);
        System.out.println(ia.getSorted());
    }

    static void testEquals(Scanner scanner) {
        int[] a = readArray(scanner);
        int[] b = readArray(scanner);
        int[] c = readArray(scanner);
        IntegerArray ia = new IntegerArray(a);
        IntegerArray ib = new IntegerArray(b);
        IntegerArray ic = new IntegerArray(c);
        System.out.println(ia.equals(ib));
        System.out.println(ia.equals(ic));
        System.out.println(ib.equals(ic));
    }

    static void testConcat(Scanner scanner) {
        int[] a = readArray(scanner);
        int[] b = readArray(scanner);
        IntegerArray array1 = new IntegerArray(a);
        IntegerArray array2 = new IntegerArray(b);
        IntegerArray concatenated = array1.concat(array2);
        System.out.println(concatenated);
    }

    static void testSimpleMethods(IntegerArray ia) {
        System.out.print(integerArrayToString(ia));
        System.out.println(ia);
        System.out.println(ia.sum());
        System.out.printf("%.2f\n", ia.average());
    }


    static String integerArrayToString(IntegerArray ia) {
        StringBuilder sb = new StringBuilder();
        sb.append(ia.length()).append('\n');
        for (int i = 0; i < ia.length(); ++i)
            sb.append(ia.getElementAt(i)).append(' ');
        sb.append('\n');
        return sb.toString();
    }

    static int[] readArray(Scanner scanner) {
        int n = scanner.nextInt();
        int[] a = new int[n];
        for (int i = 0; i < n; ++i) {
            a[i] = scanner.nextInt();
        }
        return a;
    }
    static int[] generateRandomArray(int k) {
        Random rnd = new Random(k);
        int n = rnd.nextInt(8) + 2;
        int a[] = new int[n];
        for (int i = 0; i < n; ++i) {
            a[i] = rnd.nextInt(20) - 5;
        }
        return a;
    }
}
final class IntegerArray {
    private int [] niza;
    public IntegerArray(int [] a) {
        this.niza = new int[a.length];
        for(int i=0; i<a.length;i++)
            this.niza[i] = a[i];
    }
    public int length() {
        return this.niza.length;
    }
    public int getElementAt(int i) {
        return this.niza[i];
    }
    public int sum() {
        int sum = 0;
        for(int i=0; i<this.niza.length; i++)
            sum+=this.niza[i];
        return sum;
    }
    public double average() {
        return (double)sum() / this.niza.length;
    }
    public IntegerArray getSorted() {
        IntegerArray novo = new IntegerArray(niza);
        Arrays.sort(novo.niza);
        return novo;
    }
    public IntegerArray concat(IntegerArray ia) {
        int[] nova = new int[ia.length() + this.niza.length];
        for(int i=0; i<niza.length; i++)
            nova[i]=this.niza[i];
        int j = 0;
        for(int i=this.niza.length; i<this.niza.length+ia.length(); i++)
            nova[i] = ia.getElementAt(j++);
         return new IntegerArray(nova);
    }
    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append("[");
        for(int i=0; i<this.niza.length-1; i++)
            sb.append(String.format("%d, ",niza[i]));
        sb.append(String.format("%d]", niza[niza.length-1]));
        return sb.toString();
    }

    @Override
    public boolean equals(Object obj) {
        if(((IntegerArray)obj).length() != this.length())
            return false;
        for(int i=0; i<this.niza.length;i++)
            if(((IntegerArray) obj).getElementAt(i) != this.niza[i])
                return false;
        return true;
    }
}
class ArrayReader {
    public static IntegerArray readIntegerArray(InputStream input) throws IOException {
        Scanner s = new Scanner(input);
        int n = s.nextInt();
        int [] nova = new int[n];
        for(int i=0; i<n; i++)
            nova[i] = s.nextInt();
        return new IntegerArray(nova);
    }
}