[НП] - Низа од цели броеви

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Arrays;
import java.util.Random;
import java.util.Scanner;

final class IntegerArray{
    private final int [] niza;

    public IntegerArray(int [] niza){
        this.niza=Arrays.copyOf(niza, niza.length);
    }

    public int length(){
        return niza.length;
    }

    public int getElementAt(int i){
        return niza[i];
    }

    public int sum(){
        int sum=0;
        for(int i=0;i<niza.length;i++){
            sum+=niza[i];
        }
        return sum;
    }

    public double average(){
        return (double) sum()/niza.length;
    }

    public IntegerArray getSorted(){
        int [] novaNiza=Arrays.copyOf(niza,niza.length);
        //int [] novaNiza=niza;
        Arrays.sort(novaNiza);

        return new IntegerArray(novaNiza);
    }

    public IntegerArray concat(IntegerArray ia){
        int [] novaNiza= new int [this.length()+ia.length()];
        for(int i=0;i<this.length();i++){
            novaNiza[i]=this.niza[i];
        }
        int j=0;
        for(int i=this.length();i<ia.length()+this.length();i++){
            novaNiza[i]=ia.getElementAt(j);
            j++;
        }

        return new IntegerArray(novaNiza);
    }

    @Override
    public String toString() {
        StringBuilder s=new StringBuilder();
        s.append("[");
        for(int i=0;i<this.length()-1;i++)
            s.append(niza[i]+", ");

        s.append(niza[this.length()-1]+"]");

        return s.toString();
    }

     @Override
    public boolean equals(Object o){
        if(o==this)
            return true;
        if(o==null)
            return false;
        if(getClass() != o.getClass())
            return false;

        IntegerArray other=(IntegerArray) o;
        if(this.length()!=((IntegerArray) o).length())
            return false;

        for(int i=0;i<this.length();i++){
            if(niza[i] != other.getElementAt(i))
                return false;
        }
        return true;
    }
}

class ArrayReader{
    public static IntegerArray readIntegerArray(InputStream input){
        Scanner in=new Scanner(input);
        int n=in.nextInt();

        int [] arr=new int [n];
        for(int i=0;i<n;i++){
            arr[i]=in.nextInt();
        }

        IntegerArray intArr=new IntegerArray(arr);
        return intArr;
    }
}

public class IntegerArrayTester {

    public static void main(String[] args) {
        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) {
        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;
    }

}