Question

1. Write a while loop that will let the user enter a series of integer values and compute the total values and number of values entered. An odd number will stop the loop. Display the number of iterations and the total of the values after the loop terminates.

for Loop

2. Write a for loop to display all numbers from 13 - 93 inclusive, ending in 3.

3. Write a for loop to display a string entered by the user backwards.

do Loop

4. Write a do .. loop for the random number dice problem from Chap Three. Add a counter variable that is used to count the number of times this code is executed in the loop and stops after 5 times.

roll = rand.nextInt(6) + 1;

      System.out.println(" Roll = " + roll);

ctr++;

Here is a sample output display:

The rolls are:

Roll = 3

Roll = 1

Roll = 4

Roll = 6

Roll = 4

Add a loop structure using the while loop and then add a for loop. The program should include 3 loops that do the same thing. What is the “best” loop structure to use for this problem and why?

Can you please tell me how to connect one class and where i should write in main or other class please

Answer 1

import java.util.Scanner;
import java.util.Random;

// Defines class loop
class MyLoop
{
   // Scanner class object created to accept data from console
   Scanner sc = new Scanner(System.in);

   // Random class object created
   Random rand = new Random();
  
   // Method to accept data till odd number is entered
   // Counts number of time loop iterated and total of even numbers
   void calculateSum()
   {
       // To store the number
       int no;
       // To store the loop iteration
       int count = 0;
       // To store total
       int total = 0;

       // Note: While loop is used because we don't know after how many times
       // user will enter the odd number

       // Loops till odd number
       while(true)
       {
           // Increase the counter by one
           count++;
           // Accepts a number
           System.out.print("\n Enter a number (An odd number will stop the loop): ");
           no = sc.nextInt();
           // Calculate total
           total += no;
           // Checks if the number is odd then stop the loop
           if(no % 2 == 1)              
               break;
       }
       // Displays the number of times loop iterated
       System.out.print("\n The number of iterations: " + count);
       // Displays the total
       System.out.print("\n The total of the values: " + total);
   }
  
   // Method to display all the numbers ending in 3 from 13 - 93
   void displayEndingBy3()
   {
       // Note: for loop is used because we know how many times to iterate
       // or stopping condition (93) and starting value 13
      
       // Loops from 13 to 93
       for(int c = 13; c <= 93; c++)
           // Checks if unit digit of the number is 3 then number ending in 3
           if(c % 10 == 3)
               // Display the number
               System.out.println(c);
   }

   // Method to display a string entered by the user backwards.
   void showBackward()
   {
       // Accepts a string
       System.out.print("\n Enter a string: ");
       String data = sc.next();
      
      
       System.out.println("\n Backward String: ");
       // Note: for loop is used because we know how many times to iterate
       // or stopping condition (0) and starting value length of the string minus one
      
       // Loops from length of the string -1 (last index position)
       // to 0 (first index position)
       for(int c = data.length()-1; c >= 0; c--)
           // Displays the character at c index position
           System.out.print(data.charAt(c));
   }
  
   // Method to generate random number between 1 and 6 and displays it
   void rollDice()
   {
       // Counter variable
       int ctr = 0;
      
       System.out.println("\n The rolls are: ");
      
       // Note: The best loop structure is is for loop
       // because we know how many times to iterate
      
       // Loop 5 times
       do
       {
           // Generates a random number between 1 and 6
           int roll = rand.nextInt(6) + 1;
           // Displays the number
           System.out.println(" Roll = " + roll);
           // Increase the counter by one
           ctr++;
       }while(ctr < 5); // Checks if ctr value is less than 5 then continue
   }
}// End of class

// Driver class definition
public class LoopDriver
{
   // main method definition
   public static void main(String []s)
   {
       // Creates an object of class MyLoop
       MyLoop loop = new MyLoop();
      
       System.out.println("\n ******** Calculate sum till odd number entered ******** ");
       loop.calculateSum();
      
       System.out.println("\n ******** Display numer ends in 3 from 13 - 93 ******** ");
       loop.displayEndingBy3();
      
       System.out.println("\n ******** Display string backward ******** ");
       loop.showBackward();
      
       System.out.println("\n ******** Display rolled dice value ******** ");
       loop.rollDice();
   }// End of main method
}// End of driver class

Sample Output:

******** Calculate sum till odd number entered ********

Enter a number (An odd number will stop the loop): 12

Enter a number (An odd number will stop the loop): 4

Enter a number (An odd number will stop the loop): 6

Enter a number (An odd number will stop the loop): 5

The number of iterations: 4
The total of the values: 27
******** Display numer ends in 3 from 13 - 93 ********
13
23
33
43
53
63
73
83
93

******** Display string backward ********

Enter a string: This

Backward String:
sihT
******** Display rolled dice value ********

The rolls are:
Roll = 6
Roll = 1
Roll = 2
Roll = 3
Roll = 2