Question

In Java, using only recursion. Ask the user for a list of integers. Display the greatest number in the sequence. Allow any non-integer to end the input. DO NOT USE LOOPS.

We are currently learning recursion and can only use recursion. Please provide notes so to better understand. Please describe how inputting a string will end the input section and then go on to execute what number is greater within the entire user input.

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Standard Input
5 20 5 done

Enter several numbers. Enter a non-integer to end.\n
Greatest number in that sequence is 20\n

Standard Input
57 81 24 43 9 ENTER 59 77 42 35 52 ENTER complete

Enter several numbers. Enter a non-integer to end.\n
Greatest number in that sequence is 81\n

Standard Input

35 65 86 68 81 ENTER 87 36 59 44 35 ENTER 59 10 2 31 36 ENTER 78 45 11 74 60 ENTER 73 87 6 9 94 ENTER 92 36 48 16 48 ENTER 44 9 15 76 97 ENTER 72 14 35 18 37 ENTER 60 95 5 93 64 ENTER 59 93 93 15 9 ENTER 24 33 49 11 3 ENTER 30 98 12 15 21 ENTER 34 99 87 32 19 ENTER 9 39 80 7 1 ENTER 94 76 31 65 23 ENTER 56 53 82 59 76 ENTER 80 44 42 74 62 ENTER 85 21 92 82 35 ENTER 1 37 23 38 30 ENTER 30 63 23 15 56 ENTER no

Enter several numbers. Enter a non-integer to end.\n
Greatest number in that sequence is 99\n

Answer 1

Complete code with proper commenting, Copy the code and run it into your system :

import java.util.*;

public class Main
{
//list to store all the integer values input by the user
static ArrayList<Integer> number_list = new ArrayList<Integer>();
  
//Scanner class object to get the input from User
static Scanner scan = new Scanner(System.in);
  
//Main Function
   public static void main(String[] args) {

   System.out.print("Enter Several Numbers : ");
     
   //Calling Recursive Function
   askuser();
     
     
     
   }
  
   //Recursion Function
   public static void askuser()
   {
   //taking a input from user and store it into num variable
   String num = scan.next();
  
   //We are using try, so that if user enter a non numerical value, Exception will thrown
   //catch block catches that exception, where we print the largest value in the sequence
   try {
   //Converting the string into int data type
   int n = Integer.parseInt(num);
     
   //adding the int value to the number_list
   number_list.add(n);
     
   //again running the function, recursive call
   askuser();
  
   }
   catch(Exception e) {
   //This variable will store the largest value
   int temp = 0;
  
   //iterating the number list
   for(Integer value : number_list)
   {
  
   if(temp < value)
   {
   temp = value;
   }
   }
  
   System.out.println("Largest Value in the sequence : "+ temp);
   return;
   }
  
   }
}

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Output :

Enter Several Numbers : 2 3 4 1 23 77 34 End Largest Value in the sequence : 77

Enter Several Numbers : 34 -4 22 56 99 10 12 Done Largest Value in the sequence : 99

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Explanation :

1. Arraylist<Interger> : It is a generic datatype, which takes an integer value as an input

2. In the askUser() function, we are asking an input from the user and store it into String variable

3. Now we are trying to convert the value into Integer Datatype

4. If it's succesfully converted :

4.1. we add it to the number list

4.2 And call the askUser() function again

5. If it's falied, it will throw an error which will catched in catch block

6. In catch block, we iterarte over the List and store the largest value in temp var and display it

7. at last we use return, which transfer the control back to the main function from the askuser() function.