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1
import java.util.Random;

public class A1 {
    public static void main(String[] args) {
        int[] randomArray = new int[10];
        int sum = 0;
        
        Random random = new Random();
        
        for (int i = 0; i < randomArray.length; i++) {
            randomArray[i] = random.nextInt(101);
            sum = sum + randomArray[i];
        }
        
        System.out.println("Massiv chisel: " + java.util.Arrays.toString(randomArray));
        System.out.println("Summa: " + sum);
    }
}

2 got
import java.util.Arrays;
import java.util.Scanner;
import java.util.Random;

public class A2 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        
        System.out.println("kolvo elementov: ");
        int n = scanner.nextInt();
        int[] array = new int[n];
        
        System.out.println("vvedite elementi: ");
        for (int i = 0; i < array.length; i++) {
            array[i] = scanner.nextInt();
        }
        
        System.out.println("massiv: ");
        System.out.println(Arrays.toString(array));
        
        Arrays.sort(array);
        int secondMax = array[array.length - 2];
        
        System.out.println("dtoroy po velechine: ");
        System.out.println(secondMax);
        
        scanner.close();
    }
}

3

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        int n = scanner.nextInt();
        int[] a = new int[n];

        for (int i = 0; i < n; i++) {
            a[i] = scanner.nextInt();
        }

        for (int i = 0; i < n; i++) {
            int count = 0;

            for (int j = 0; j < n; j++) {
                if (a[i] == a[j]) {
                    count++;
                }
            }

            if (count == 1) {
                System.out.print(a[i] + " ");
            }
        }
    }
}

4 
import java.util.Random;
import java.util.Arrays;

public class A4 {
    public static void main(String[] args) {
        Random random = new Random();
        
        int[] array = new int[10];
        
        for (int i = 0; i < array.length; i++) {
            array[i] = random.nextInt(100);
        }
        
        System.out.println("Massiv: " + Arrays.toString(array));
        
        int reverse [] = new int[array.length];
        for (int i = 0; i<array.length; i++) {
            reverse[i] = array[array.length - 1 - i];
        }
        System.out.println("Perevernytiy: " + Arrays.toString(reverse));
    }
}

5
import java.util.Scanner;
import java.util.Arrays;

public class A5 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        
        System.out.println("kolvo elementov: ");
        int num = scanner.nextInt();
        int[] array = new int[num];
        
        System.out.println("elementi: ");
        for (int i = 0; i < array.length; i++) {
            array[i] = scanner.nextInt();
        }
        
        System.out.println("massiv:");
        System.out.println(Arrays.toString(array));
        
        for (int i = 0; i < array.length - 1; i += 2) {
            int temp = array[i];
            array[i] = array[i + 1];
            array[i + 1] = temp;
        }
        System.out.println("perestavlenniy: ");
        System.out.println(Arrays.toString(array));
        
        scanner.close();
    }
}