Question

Exercise 3: Work exercise 11.4, 11.12, and 11.14 into one program (to develop 3 methods for ArrayList: first method finds the maximum element in an array list; the second method computes the sum of all elements in an array list; and the third method combines (union) two lists by adding the second list to the first list). Use Integer type for all methods. See problem statements for methods signatures and sample test data. Write one separate test program to test all three methods. 11.4 (Maximum element in ArrayList) Write the following method that returns the maximum value in an ArrayList of integers. The method returns null if the list is null or the list size is 0. public static Integer max(ArrayList list) Write a test program that prompts the user to enter a sequence of numbers ending with 0, and invokes this method to return the largest number in the input. 11.12 (Sum ArrayList) Write the following method that returns the sum of all numbers in an ArrayList: public static double sum(ArrayList list) Write a test program that prompts the user to enter 5 numbers, stores them in an array list, and displays their sum. 11.14 (Combine two lists) Write a method that returns the union of two array lists of integers using the following header: public static ArrayList union( ArrayList list1, ArrayList list2) For example, the union of two array lists {2, 3, 1, 5} and {3, 4, 6} is {2, 3, 1, 5, 3, 4, 6}. Write a test program that prompts the user to enter two lists, each with five integers, and displays their union. The numbers are separated by exactly one space in the output. Here is a sample run: Enter five integers for list1: 3 5 45 4 3 Enter five integers for list2: 33 51 5 4 13 The combined list is 3 5 45 4 3 33 51 5 4 13

Answer 1

import java.util.ArrayList;
import java.util.Scanner;

public class ArrayListMax {

    public static Integer max(ArrayList<Integer> list) {
        int max = list.get(0);
        for(int i = 0; i < list.size(); ++i) {
            if(list.get(i) > max) {
                max = list.get(i);
            }
        }
        return max;
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter integers(0 to stop): ");
        ArrayList<Integer> list = new ArrayList<Integer>();
        int num;
        while (true) {
            num = in.nextInt();
            if(num == 0) {
                break;
            }
            list.add(num);
        }
        System.out.println("Maximum number in " + list + " is " + max(list));
    }

}

Enter integers (0 to stop): 21 29 27 Maximum number in [23, 21, 29, 27] is 29 Process finished with e xit code 0

import java.util.ArrayList;
import java.util.Scanner;

public class ArrayListSum {

    public static double sum(ArrayList<Integer> list) {
        int total = 0;
        for(int i = 0; i < list.size(); ++i) {
            total += list.get(i);
        }
        return total;
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter 5 numbers: ");
        ArrayList<Integer> list = new ArrayList<Integer>();
        for(int i = 0; i < 5; ++i) {
            list.add(in.nextInt());
        }
        System.out.println("sum of numbers in " + list + " is " + sum(list));
    }

}

Enter 5 numbers: sum of numbers in [1, 2, 3, 4, 5] is 15.0 Process finished with e xit code 0

import java.util.ArrayList;
import java.util.Scanner;

public class ArrayListCombine {

    public static ArrayList<Integer> union(ArrayList<Integer> list1, ArrayList<Integer> list2) {
        ArrayList<Integer> ret = new ArrayList<Integer>();
        for(int i = 0; i < list2.size(); ++i) {
            ret.add(list1.get(i));
        }
        for(int i = 0; i < list2.size(); ++i) {
            ret.add(list2.get(i));
        }
        return ret;
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter five integers for list1: ");
        ArrayList<Integer> list1 = new ArrayList<Integer>();
        ArrayList<Integer> list2 = new ArrayList<Integer>();
        for(int i = 0; i < 5; ++i) {
            list1.add(in.nextInt());
        }
        System.out.print("Enter five integers for list2: ");
        for(int i = 0; i < 5; ++i) {
            list2.add(in.nextInt());
        }
        ArrayList<Integer> combined = union(list1, list2);
        System.out.print("The combined list is ");
        for(int i = 0; i < combined.size(); ++i) {
            System.out.print(combined.get(i) + " ");
        }
        System.out.println();
    }

}

Enter five integers for listl: aris:r i::і:W: :utíxyrer2x İ.YKr :Lim::: 33 51 5 4 13 The combined list is 3 5 45 4 3 33 51 5 4 13 Process finished with e xit code 0